Replace NetMQ with custom TCP networking

Agent/Phantom.Agent.Services/Rpc/ControllerConnection.cs

@@ -1,19 +1,19 @@
 using Phantom.Common.Messages.Agent;
 using Phantom.Utils.Actor;
-using Phantom.Utils.Rpc.Runtime;
+using Phantom.Utils.Rpc.Message;
 
 namespace Phantom.Agent.Services.Rpc;
 
-public sealed class ControllerConnection(RpcSendChannel<IMessageToController> sendChannel) {
+public sealed class ControllerConnection(MessageSender<IMessageToController> sender) {
 	internal bool TrySend<TMessage>(TMessage message) where TMessage : IMessageToController {
-		return sendChannel.TrySendMessage(message);
+		return sender.TrySend(message);
 	}
 	
 	internal ValueTask Send<TMessage>(TMessage message, CancellationToken cancellationToken) where TMessage : IMessageToController {
-		return sendChannel.SendMessage(message, cancellationToken);
+		return sender.Send(message, cancellationToken);
 	}
 	
 	internal Task<TReply> Send<TMessage, TReply>(TMessage message, TimeSpan waitForReplyTime, CancellationToken cancellationToken) where TMessage : IMessageToController, ICanReply<TReply> {
-		return sendChannel.SendMessage<TMessage, TReply>(message, waitForReplyTime, cancellationToken);
+		return sender.Send<TMessage, TReply>(message, waitForReplyTime, cancellationToken);
 	}
 }

Agent/Phantom.Agent/Program.cs

@@ -10,6 +10,7 @@ using Phantom.Common.Messages.Agent.ToController;
 using Phantom.Utils.Actor;
 using Phantom.Utils.Logging;
 using Phantom.Utils.Rpc.Message;
+using Phantom.Utils.Rpc.Runtime;
 using Phantom.Utils.Rpc.Runtime.Client;
 using Phantom.Utils.Runtime;
 using Phantom.Utils.Threading;
@@ -60,8 +61,12 @@ try {
 		CertificateThumbprint: agentKey.Value.CertificateThumbprint,
 		AuthToken: agentKey.Value.AuthToken,
 		Handshake: controllerHandshake,
-		SendQueueCapacity: 500,
-		PingInterval: TimeSpan.FromSeconds(10)
+		CommonParameters: new RpcCommonConnectionParameters(
+			MessageQueueCapacity: 250,
+			FrameQueueCapacity: 500,
+			MaxConcurrentlyHandledMessages: 50,
+			PingInterval: TimeSpan.FromSeconds(10)
+		)
 	);
 	
 	using var rpcClient = await RpcClient<IMessageToController, IMessageToAgent>.Connect("Controller", rpcClientConnectionParameters, AgentMessageRegistries.Definitions, shutdownCancellationToken);
@@ -74,7 +79,7 @@ try {
 	try {
 		PhantomLogger.Root.InformationHeading("Launching Phantom Panel agent...");
 		
-		var agentServices = new AgentServices(agentInfo, folders, new AgentServiceConfiguration(maxConcurrentBackupCompressionTasks), new ControllerConnection(rpcClient.SendChannel), javaRuntimeRepository);
+		var agentServices = new AgentServices(agentInfo, folders, new AgentServiceConfiguration(maxConcurrentBackupCompressionTasks), new ControllerConnection(rpcClient.MessageSender), javaRuntimeRepository);
 		
 		var rpcMessageHandlerInit = new ControllerMessageHandlerActor.Init(agentServices);
 		var rpcMessageHandlerActor = agentServices.ActorSystem.ActorOf(ControllerMessageHandlerActor.Factory(rpcMessageHandlerInit), "ControllerMessageHandler");
@@ -91,7 +96,7 @@ try {
 		PhantomLogger.Root.Information("Unregistering agent...");
 		try {
 			using var unregisterCancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(10));
-			await rpcClient.SendChannel.SendMessage(new UnregisterAgentMessage(), unregisterCancellationTokenSource.Token);
+			await rpcClient.MessageSender.Send(new UnregisterAgentMessage(), unregisterCancellationTokenSource.Token);
 		} catch (OperationCanceledException) {
 			PhantomLogger.Root.Warning("Could not unregister agent after shutdown.");
 		} catch (Exception e) {

Controller/Phantom.Controller.Services/Agents/AgentConnection.cs

@@ -41,7 +41,7 @@ sealed class AgentConnection(Guid agentGuid, string agentName) {
 	public ValueTask Send<TMessage>(TMessage message) where TMessage : IMessageToAgent {
 		lock (this) {
 			if (connection != null) {
-				return connection.SendChannel.SendMessage(message);
+				return connection.MessageSender.Send(message);
 			}
 		}
 		
@@ -52,7 +52,7 @@ sealed class AgentConnection(Guid agentGuid, string agentName) {
 	public Task<TReply?> Send<TMessage, TReply>(TMessage message, TimeSpan waitForReplyTime, CancellationToken waitForReplyCancellationToken) where TMessage : IMessageToAgent, ICanReply<TReply> where TReply : class {
 		lock (this) {
 			if (connection != null) {
-				return connection.SendChannel.SendMessage<TMessage, TReply>(message, waitForReplyTime, waitForReplyCancellationToken)!;
+				return connection.MessageSender.Send<TMessage, TReply>(message, waitForReplyTime, waitForReplyCancellationToken)!;
 			}
 		}
 		

Controller/Phantom.Controller.Services/Rpc/WebMessageDataUpdateSenderActor.cs

@@ -5,24 +5,24 @@ using Phantom.Common.Messages.Web;
 using Phantom.Common.Messages.Web.ToWeb;
 using Phantom.Controller.Services.Instances;
 using Phantom.Utils.Actor;
-using Phantom.Utils.Rpc.Runtime;
+using Phantom.Utils.Rpc.Message;
 
 namespace Phantom.Controller.Services.Rpc;
 
 sealed class WebMessageDataUpdateSenderActor : ReceiveActor<WebMessageDataUpdateSenderActor.ICommand> {
-	public readonly record struct Init(RpcSendChannel<IMessageToWeb> Connection, ControllerState ControllerState, InstanceLogManager InstanceLogManager);
+	public readonly record struct Init(MessageSender<IMessageToWeb> MessageSender, ControllerState ControllerState, InstanceLogManager InstanceLogManager);
 	
 	public static Props<ICommand> Factory(Init init) {
 		return Props<ICommand>.Create(() => new WebMessageDataUpdateSenderActor(init), new ActorConfiguration { SupervisorStrategy = SupervisorStrategies.Resume });
 	}
 	
-	private readonly RpcSendChannel<IMessageToWeb> connection;
+	private readonly MessageSender<IMessageToWeb> messageSender;
 	private readonly ControllerState controllerState;
 	private readonly InstanceLogManager instanceLogManager;
 	private readonly ActorRef<ICommand> selfCached;
 	
 	private WebMessageDataUpdateSenderActor(Init init) {
-		this.connection = init.Connection;
+		this.messageSender = init.MessageSender;
 		this.controllerState = init.ControllerState;
 		this.instanceLogManager = init.InstanceLogManager;
 		this.selfCached = SelfTyped;
@@ -70,18 +70,18 @@ sealed class WebMessageDataUpdateSenderActor : ReceiveActor<WebMessageDataUpdate
 	private sealed record RefreshUserSessionCommand(Guid UserGuid) : ICommand;
 	
 	private Task RefreshAgents(RefreshAgentsCommand command) {
-		return connection.SendMessage(new RefreshAgentsMessage(command.Agents.Values.ToImmutableArray())).AsTask();
+		return messageSender.Send(new RefreshAgentsMessage(command.Agents.Values.ToImmutableArray())).AsTask();
 	}
 	
 	private Task RefreshInstances(RefreshInstancesCommand command) {
-		return connection.SendMessage(new RefreshInstancesMessage(command.Instances.Values.ToImmutableArray())).AsTask();
+		return messageSender.Send(new RefreshInstancesMessage(command.Instances.Values.ToImmutableArray())).AsTask();
 	}
 	
 	private Task ReceiveInstanceLogs(ReceiveInstanceLogsCommand command) {
-		return connection.SendMessage(new InstanceOutputMessage(command.InstanceGuid, command.Lines)).AsTask();
+		return messageSender.Send(new InstanceOutputMessage(command.InstanceGuid, command.Lines)).AsTask();
 	}
 	
 	private Task RefreshUserSession(RefreshUserSessionCommand command) {
-		return connection.SendMessage(new RefreshUserSessionMessage(command.UserGuid)).AsTask();
+		return messageSender.Send(new RefreshUserSessionMessage(command.UserGuid)).AsTask();
 	}
 }

Controller/Phantom.Controller.Services/Rpc/WebMessageHandlerActor.cs

@@ -63,7 +63,7 @@ sealed class WebMessageHandlerActor : ReceiveActor<IMessageToController> {
 		this.minecraftVersions = init.MinecraftVersions;
 		this.eventLogManager = init.EventLogManager;
 		
-		var senderActorInit = new WebMessageDataUpdateSenderActor.Init(connection.SendChannel, controllerState, init.InstanceLogManager);
+		var senderActorInit = new WebMessageDataUpdateSenderActor.Init(connection.MessageSender, controllerState, init.InstanceLogManager);
 		Context.ActorOf(WebMessageDataUpdateSenderActor.Factory(senderActorInit), "DataUpdateSender");
 		
 		ReceiveAsync<UnregisterWebMessage>(HandleUnregisterWeb);

Controller/Phantom.Controller/Program.cs

@@ -6,6 +6,7 @@ using Phantom.Controller.Database.Postgres;
 using Phantom.Controller.Services;
 using Phantom.Utils.IO;
 using Phantom.Utils.Logging;
+using Phantom.Utils.Rpc.Runtime;
 using Phantom.Utils.Rpc.Runtime.Server;
 using Phantom.Utils.Runtime;
 using Phantom.Utils.Tasks;
@@ -64,16 +65,24 @@ try {
 		EndPoint: agentRpcServerHost,
 		Certificate: agentKeyData.Certificate,
 		AuthToken: agentKeyData.AuthToken,
-		SendQueueCapacity: 100,
-		PingInterval: TimeSpan.FromSeconds(10)
+		CommonParameters: new RpcCommonConnectionParameters(
+			MessageQueueCapacity: 50,
+			FrameQueueCapacity: 100,
+			MaxConcurrentlyHandledMessages: 20,
+			PingInterval: TimeSpan.FromSeconds(10)
+		)
 	);
 	
 	var webConnectionParameters = new RpcServerConnectionParameters(
 		EndPoint: webRpcServerHost,
 		Certificate: webKeyData.Certificate,
 		AuthToken: webKeyData.AuthToken,
-		SendQueueCapacity: 500,
-		PingInterval: TimeSpan.FromMinutes(1)
+		CommonParameters: new RpcCommonConnectionParameters(
+			MessageQueueCapacity: 250,
+			FrameQueueCapacity: 500,
+			MaxConcurrentlyHandledMessages: 100,
+			PingInterval: TimeSpan.FromMinutes(1)
+		)
 	);
 	
 	LinkedTasks<bool> rpcServerTasks = new LinkedTasks<bool>([

Utils/Phantom.Utils.Rpc/Frame/IFrame.cs

@@ -6,12 +6,14 @@ interface IFrame {
 	private const byte TypePingId = 0;
 	private const byte TypePongId = 1;
 	private const byte TypeMessageId = 2;
-	private const byte TypeReplyId = 3;
-	private const byte TypeErrorId = 4;
+	private const byte TypeAcknowledgmentId = 3;
+	private const byte TypeReplyId = 4;
+	private const byte TypeErrorId = 5;
 	
 	static readonly ReadOnlyMemory<byte> TypePing = new ([TypePingId]);
 	static readonly ReadOnlyMemory<byte> TypePong = new ([TypePongId]);
 	static readonly ReadOnlyMemory<byte> TypeMessage = new ([TypeMessageId]);
+	static readonly ReadOnlyMemory<byte> TypeAcknowledgment = new ([TypeAcknowledgmentId]);
 	static readonly ReadOnlyMemory<byte> TypeReply = new ([TypeReplyId]);
 	static readonly ReadOnlyMemory<byte> TypeError = new ([TypeErrorId]);
 	
@@ -37,6 +39,11 @@ interface IFrame {
 					await reader.OnMessageFrame(messageFrame, cancellationToken);
 					break;
 				
+				case TypeAcknowledgmentId:
+					var acknowledgmentFrame = await AcknowledgmentFrame.Read(stream, cancellationToken);
+					reader.OnAcknowledgmentFrame(acknowledgmentFrame);
+					break;
+				
 				case TypeReplyId:
 					var replyFrame = await ReplyFrame.Read(stream, cancellationToken);
 					reader.OnReplyFrame(replyFrame);

Utils/Phantom.Utils.Rpc/Frame/IFrameReader.cs

@@ -6,6 +6,7 @@ interface IFrameReader {
 	ValueTask OnPingFrame(DateTimeOffset pingTime, CancellationToken cancellationToken);
 	void OnPongFrame(PongFrame frame);
 	Task OnMessageFrame(MessageFrame frame, CancellationToken cancellationToken);
+	void OnAcknowledgmentFrame(AcknowledgmentFrame frame);
 	void OnReplyFrame(ReplyFrame frame);
 	void OnErrorFrame(ErrorFrame frame);
 	void OnUnknownFrameId(byte frameId);

Utils/Phantom.Utils.Rpc/Frame/Types/AcknowledgmentFrame.cs

@@ -0,0 +1,18 @@
+using Phantom.Utils.Rpc.Runtime;
+
+namespace Phantom.Utils.Rpc.Frame.Types;
+
+sealed record AcknowledgmentFrame(uint FirstMessageId, uint LastMessageId) : IFrame {
+	public ReadOnlyMemory<byte> FrameType => IFrame.TypeAcknowledgment;
+	
+	public async Task Write(Stream stream, CancellationToken cancellationToken = default) {
+		await RpcSerialization.WriteUnsignedInt(FirstMessageId, stream, cancellationToken);
+		await RpcSerialization.WriteUnsignedInt(LastMessageId, stream, cancellationToken);
+	}
+	
+	public static async Task<AcknowledgmentFrame> Read(Stream stream, CancellationToken cancellationToken) {
+		var firstMessageId = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
+		var lastMessageId = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
+		return new AcknowledgmentFrame(firstMessageId, lastMessageId);
+	}
+}

Utils/Phantom.Utils.Rpc/Frame/Types/MessageFrame.cs

@@ -8,30 +8,26 @@ sealed record MessageFrame(uint MessageId, ushort RegistryCode, ReadOnlyMemory<b
 	public ReadOnlyMemory<byte> FrameType => IFrame.TypeMessage;
 	
 	public async Task Write(Stream stream, CancellationToken cancellationToken) {
-		int serializedMessageLength = SerializedMessage.Length;
+		uint serializedMessageLength = (uint) SerializedMessage.Length;
 		CheckMessageLength(serializedMessageLength);
 		
 		await RpcSerialization.WriteUnsignedInt(MessageId, stream, cancellationToken);
 		await RpcSerialization.WriteUnsignedShort(RegistryCode, stream, cancellationToken);
-		await RpcSerialization.WriteSignedInt(serializedMessageLength, stream, cancellationToken);
+		await RpcSerialization.WriteUnsignedInt(serializedMessageLength, stream, cancellationToken);
 		await stream.WriteAsync(SerializedMessage, cancellationToken);
 	}
 	
 	public static async Task<MessageFrame> Read(Stream stream, CancellationToken cancellationToken) {
 		var messageId = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
 		var registryCode = await RpcSerialization.ReadUnsignedShort(stream, cancellationToken);
-		var serializedMessageLength = await RpcSerialization.ReadSignedInt(stream, cancellationToken);
+		var serializedMessageLength = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
 		CheckMessageLength(serializedMessageLength);
 		var serializedMessage = await RpcSerialization.ReadBytes(serializedMessageLength, stream, cancellationToken);
 		
 		return new MessageFrame(messageId, registryCode, serializedMessage);
 	}
 	
-	private static void CheckMessageLength(int messageLength) {
-		if (messageLength < 0) {
-			throw new RpcErrorException("Message length is negative.", RpcError.InvalidData);
-		}
-		
+	private static void CheckMessageLength(uint messageLength) {
 		if (messageLength > MaxMessageBytes) {
 			throw new RpcErrorException("Message is too large: " + messageLength + " > " + MaxMessageBytes + " bytes", RpcError.MessageTooLarge);
 		}

Utils/Phantom.Utils.Rpc/Frame/Types/ReplyFrame.cs

@@ -8,30 +8,26 @@ sealed record ReplyFrame(uint ReplyingToMessageId, ReadOnlyMemory<byte> Serializ
 	public ReadOnlyMemory<byte> FrameType => IFrame.TypeReply;
 	
 	public async Task Write(Stream stream, CancellationToken cancellationToken) {
-		int replyLength = SerializedReply.Length;
-		CheckReplyLength(replyLength);
+		uint serializedReplyLength = (uint) SerializedReply.Length;
+		CheckReplyLength(serializedReplyLength);
 		
 		await RpcSerialization.WriteUnsignedInt(ReplyingToMessageId, stream, cancellationToken);
-		await RpcSerialization.WriteSignedInt(replyLength, stream, cancellationToken);
+		await RpcSerialization.WriteUnsignedInt(serializedReplyLength, stream, cancellationToken);
 		await stream.WriteAsync(SerializedReply, cancellationToken);
 	}
 	
 	public static async Task<ReplyFrame> Read(Stream stream, CancellationToken cancellationToken) {
 		var replyingToMessageId = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
-		var replyLength = await RpcSerialization.ReadSignedInt(stream, cancellationToken);
-		CheckReplyLength(replyLength);
-		var reply = await RpcSerialization.ReadBytes(replyLength, stream, cancellationToken);
+		var serializedReplyLength = await RpcSerialization.ReadUnsignedInt(stream, cancellationToken);
+		CheckReplyLength(serializedReplyLength);
+		var serializedReply = await RpcSerialization.ReadBytes(serializedReplyLength, stream, cancellationToken);
 		
-		return new ReplyFrame(replyingToMessageId, reply);
+		return new ReplyFrame(replyingToMessageId, serializedReply);
 	}
 	
-	private static void CheckReplyLength(int replyLength) {
-		if (replyLength < 0) {
-			throw new RpcErrorException("Reply length is negative.", RpcError.InvalidData);
-		}
-		
+	private static void CheckReplyLength(uint replyLength) {
 		if (replyLength > MaxReplyBytes) {
-			throw new RpcErrorException("Reply is too large: " + replyLength + " > " + MaxReplyBytes + " bytes", RpcError.MessageTooLarge);
+			throw new RpcErrorException("Reply is too large: " + replyLength + " > " + MaxReplyBytes + " bytes", RpcError.ReplyTooLarge);
 		}
 	}
 }

Utils/Phantom.Utils.Rpc/Handshake/IRpcHandshake.cs

@@ -1,6 +0,0 @@
-namespace Phantom.Utils.Rpc.Handshake;
-
-public interface IRpcHandshake<T> {
-	Task Send(Stream stream, CancellationToken cancellationToken);
-	Task<T> Receive(Stream stream, CancellationToken cancellationToken);
-}

Utils/Phantom.Utils.Rpc/Handshake/RpcFinalHandshakeResult.cs

@@ -0,0 +1,7 @@
+namespace Phantom.Utils.Rpc.Handshake;
+
+public enum RpcFinalHandshakeResult : byte {
+	Error = 0,
+	NewSession = 1,
+	ReusedSession = 2,
+}

Utils/Phantom.Utils.Rpc/Message/IMessageReplySender.cs

@@ -1,6 +1,9 @@
-namespace Phantom.Utils.Rpc.Runtime;
+using Phantom.Utils.Rpc.Runtime;
 
-interface IRpcReplySender {
+namespace Phantom.Utils.Rpc.Message;
+
+interface IMessageReplySender {
+	ValueTask SendEmptyReply(uint replyingToMessageId, CancellationToken cancellationToken);
 	ValueTask SendReply<TReply>(uint replyingToMessageId, TReply reply, CancellationToken cancellationToken);
 	ValueTask SendError(uint replyingToMessageId, RpcError error, CancellationToken cancellationToken);
 }

Utils/Phantom.Utils.Rpc/Message/MessageAcknowledgmentQueue.cs

@@ -0,0 +1,39 @@
+using Phantom.Utils.Collections;
+using Phantom.Utils.Rpc.Frame.Types;
+using Phantom.Utils.Threading;
+
+namespace Phantom.Utils.Rpc.Message;
+
+sealed class MessageAcknowledgmentQueue {
+	private readonly Lock @lock = new ();
+	private readonly RangeSet<uint> pendingMessageIdRanges = new ();
+	private readonly ManualResetEventSlim pendingEvent = new ();
+	
+	public void Enqueue(uint messageId) {
+		lock (@lock) {
+			pendingMessageIdRanges.Add(messageId);
+		}
+		
+		pendingEvent.Set();
+	}
+	
+	public Task Wait(CancellationToken cancellationToken) {
+		return pendingEvent.WaitHandle.WaitOneAsync(cancellationToken);
+	}
+	
+	public List<AcknowledgmentFrame> Drain() {
+		pendingEvent.Reset();
+		
+		List<AcknowledgmentFrame> frames = [];
+		
+		lock (@lock) {
+			foreach (var range in pendingMessageIdRanges) {
+				frames.Add(new AcknowledgmentFrame(range.Min, range.Max));
+			}
+			
+			pendingMessageIdRanges.Clear();
+		}
+		
+		return frames;
+	}
+}

Utils/Phantom.Utils.Rpc/Message/MessageHandler.cs

@@ -0,0 +1,23 @@
+using Phantom.Utils.Rpc.Runtime;
+
+namespace Phantom.Utils.Rpc.Message;
+
+sealed class MessageHandler<TMessageBase>(IMessageReceiver<TMessageBase> messageReceiver, IMessageReplySender replySender) {
+	public IMessageReceiver<TMessageBase> Receiver => messageReceiver;
+	
+	public void OnPing() {
+		messageReceiver.OnPing();
+	}
+	
+	public ValueTask SendEmptyReply(uint messageId, CancellationToken cancellationToken) {
+		return replySender.SendEmptyReply(messageId, cancellationToken);
+	}
+	
+	public ValueTask SendReply<TReply>(uint messageId, TReply reply, CancellationToken cancellationToken) {
+		return replySender.SendReply(messageId, reply, cancellationToken);
+	}
+	
+	public ValueTask SendError(uint messageId, RpcError error, CancellationToken cancellationToken) {
+		return replySender.SendError(messageId, error, cancellationToken);
+	}
+}

Utils/Phantom.Utils.Rpc/Message/MessageReceiveTracker.cs

@@ -6,7 +6,6 @@ sealed class MessageReceiveTracker {
 	private readonly RangeSet<uint> receivedMessageIds = new ();
 	
 	public bool ReceiveMessage(uint messageId) {
-		// TODO reset on session change and invalidate replies
 		lock (receivedMessageIds) {
 			return receivedMessageIds.Add(messageId);
 		}

Utils/Phantom.Utils.Rpc/Message/MessageRegistry.cs

@@ -9,7 +9,7 @@ namespace Phantom.Utils.Rpc.Message;
 public sealed class MessageRegistry<TMessageBase>(ILogger logger) {
 	private readonly Dictionary<Type, ushort> typeToCodeMapping = new ();
 	private readonly Dictionary<ushort, Type> codeToTypeMapping = new ();
-	private readonly Dictionary<ushort, Func<uint, ReadOnlyMemory<byte>, RpcMessageHandler<TMessageBase>, CancellationToken, Task>> codeToHandlerMapping = new ();
+	private readonly Dictionary<ushort, Func<uint, ReadOnlyMemory<byte>, MessageHandler<TMessageBase>, CancellationToken, Task>> codeToHandlerMapping = new ();
 	
 	public void Add<TMessage>(ushort code) where TMessage : TMessageBase {
 		if (HasReplyType(typeof(TMessage))) {
@@ -50,7 +50,7 @@ public sealed class MessageRegistry<TMessageBase>(ILogger logger) {
 		}
 	}
 	
-	internal async Task Handle(MessageFrame frame, RpcMessageHandler<TMessageBase> handler, CancellationToken cancellationToken) {
+	internal async Task Handle(MessageFrame frame, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) {
 		uint messageId = frame.MessageId;
 		
 		if (codeToHandlerMapping.TryGetValue(frame.RegistryCode, out var action)) {
@@ -62,26 +62,35 @@ public sealed class MessageRegistry<TMessageBase>(ILogger logger) {
 		}
 	}
 	
-	private async Task DeserializationHandler<TMessage>(uint messageId, ReadOnlyMemory<byte> serializedMessage, RpcMessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase {
+	private async Task DeserializationHandler<TMessage>(uint messageId, ReadOnlyMemory<byte> serializedMessage, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase {
 		TMessage message;
 		try {
 			message = RpcSerialization.Deserialize<TMessage>(serializedMessage);
 		} catch (Exception e) {
-			logger.Error(e, "Could not deserialize message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
-			await handler.SendError(messageId, RpcError.MessageDeserializationError, cancellationToken);
+			await OnMessageDeserializationError<TMessage>(messageId, e, handler, cancellationToken);
 			return;
 		}
 		
-		handler.Receiver.OnMessage(message);
+		try {
+			handler.Receiver.OnMessage(message);
+		} catch (Exception e) {
+			await OnMessageHandlingError<TMessage>(messageId, e, handler, cancellationToken);
+			return;
+		}
+		
+		try {
+			await handler.SendEmptyReply(messageId, cancellationToken);
+		} catch (Exception e) {
+			await OnMessageReplyingError<TMessage>(messageId, e, handler, cancellationToken);
+		}
 	}
 	
-	private async Task DeserializationHandler<TMessage, TReply>(uint messageId, ReadOnlyMemory<byte> serializedMessage, RpcMessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase, ICanReply<TReply> {
+	private async Task DeserializationHandler<TMessage, TReply>(uint messageId, ReadOnlyMemory<byte> serializedMessage, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase, ICanReply<TReply> {
 		TMessage message;
 		try {
 			message = RpcSerialization.Deserialize<TMessage>(serializedMessage);
 		} catch (Exception e) {
-			logger.Error(e, "Could not deserialize message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
-			await handler.SendError(messageId, RpcError.MessageDeserializationError, cancellationToken);
+			await OnMessageDeserializationError<TMessage>(messageId, e, handler, cancellationToken);
 			return;
 		}
 		
@@ -89,16 +98,29 @@ public sealed class MessageRegistry<TMessageBase>(ILogger logger) {
 		try {
 			reply = await handler.Receiver.OnMessage<TMessage, TReply>(message, cancellationToken);
 		} catch (Exception e) {
-			logger.Error(e, "Could not handle message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
-			await handler.SendError(messageId, RpcError.MessageHandlingError, cancellationToken);
+			await OnMessageHandlingError<TMessage>(messageId, e, handler, cancellationToken);
 			return;
 		}
 		
 		try {
 			await handler.SendReply(messageId, reply, cancellationToken);
 		} catch (Exception e) {
-			logger.Error(e, "Could not reply to message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
-			await handler.SendError(messageId, RpcError.MessageHandlingError, cancellationToken);
+			await OnMessageReplyingError<TMessage>(messageId, e, handler, cancellationToken);
 		}
 	}
+	
+	private async Task OnMessageDeserializationError<TMessage>(uint messageId, Exception exception, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase {
+		logger.Error(exception, "Could not deserialize message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
+		await handler.SendError(messageId, RpcError.MessageDeserializationError, cancellationToken);
+	}
+	
+	private async Task OnMessageHandlingError<TMessage>(uint messageId, Exception exception, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase {
+		logger.Error(exception, "Could not handle message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
+		await handler.SendError(messageId, RpcError.MessageHandlingError, cancellationToken);
+	}
+	
+	private async Task OnMessageReplyingError<TMessage>(uint messageId, Exception exception, MessageHandler<TMessageBase> handler, CancellationToken cancellationToken) where TMessage : TMessageBase {
+		logger.Error(exception, "Could not reply to message {MessageId} ({MessageType}).", messageId, typeof(TMessage).Name);
+		await handler.SendError(messageId, RpcError.MessageReplyingError, cancellationToken);
+	}
 }

Utils/Phantom.Utils.Rpc/Message/MessageReplyTracker.cs

@@ -20,30 +20,30 @@ sealed class MessageReplyTracker {
 	
 	public async Task<TReply> WaitForReply<TReply>(uint messageId, TimeSpan waitForReplyTime, CancellationToken cancellationToken) {
 		if (!replyTasks.TryGetValue(messageId, out var completionSource)) {
-			logger.Warning("No reply callback for id {MessageId}.", messageId);
-			throw new ArgumentException("No reply callback for id: " + messageId, nameof(messageId));
+			logger.Warning("No reply callback for message {MessageId}.", messageId);
+			throw new ArgumentException("No reply callback for message: " + messageId, nameof(messageId));
 		}
 		
 		try {
 			ReadOnlyMemory<byte> serializedReply = await completionSource.Task.WaitAsync(waitForReplyTime, cancellationToken);
 			return RpcSerialization.Deserialize<TReply>(serializedReply);
 		} catch (TimeoutException) {
-			logger.Debug("Timed out waiting for reply with id {MessageId}.", messageId);
+			logger.Debug("Timed out waiting for reply with message {MessageId}.", messageId);
 			throw;
 		} catch (OperationCanceledException) {
-			logger.Debug("Cancelled waiting for reply with id {MessageId}.", messageId);
+			logger.Debug("Cancelled waiting for reply with message {MessageId}.", messageId);
 			throw;
 		} catch (Exception e) {
-			logger.Warning(e, "Error processing reply with id {MessageId}.", messageId);
+			logger.Warning(e, "Error processing reply with message {MessageId}.", messageId);
 			throw;
 		} finally {
 			ForgetReply(messageId);
 		}
 	}
 	
-	public void ForgetReply(uint messageId) {
+	public void ReceiveReply(uint messageId, ReadOnlyMemory<byte> serializedReply) {
 		if (replyTasks.TryRemove(messageId, out var task)) {
-			task.SetCanceled();
+			task.SetResult(serializedReply);
 		}
 	}
 	
@@ -53,12 +53,9 @@ sealed class MessageReplyTracker {
 		}
 	}
 	
-	public void ReceiveReply(uint messageId, ReadOnlyMemory<byte> serializedReply) {
+	public void ForgetReply(uint messageId) {
 		if (replyTasks.TryRemove(messageId, out var task)) {
-			task.SetResult(serializedReply);
-		}
-		else {
-			logger.Warning("Received a reply with id {MessageId} but no registered callback.", messageId);
+			task.SetCanceled();
 		}
 	}
 }

Utils/Phantom.Utils.Rpc/Message/MessageSender.cs

@@ -0,0 +1,117 @@
+using System.Threading.Channels;
+using Phantom.Utils.Actor;
+using Phantom.Utils.Logging;
+using Phantom.Utils.Rpc.Frame.Types;
+using Phantom.Utils.Rpc.Runtime;
+using Serilog;
+
+namespace Phantom.Utils.Rpc.Message;
+
+public sealed class MessageSender<TMessageBase> {
+	private readonly ILogger logger;
+	private readonly MessageRegistry<TMessageBase> messageRegistry;
+	private readonly MessageReplyTracker messageReplyTracker;
+	private uint nextMessageId;
+	
+	private readonly Channel<PreparedMessage> messageQueue;
+	private readonly Task messageQueueTask;
+	
+	private readonly CancellationTokenSource shutdownCancellationTokenSource = new ();
+	
+	internal MessageSender(string loggerName, MessageRegistry<TMessageBase> messageRegistry, RpcCommonConnectionParameters connectionParameters) {
+		this.logger = PhantomLogger.Create<MessageSender<TMessageBase>>(loggerName);
+		this.messageRegistry = messageRegistry;
+		this.messageReplyTracker = new MessageReplyTracker(loggerName);
+		
+		this.messageQueue = Channel.CreateBounded<PreparedMessage>(new BoundedChannelOptions(connectionParameters.MessageQueueCapacity) {
+			AllowSynchronousContinuations = false,
+			FullMode = BoundedChannelFullMode.Wait,
+			SingleReader = true,
+			SingleWriter = false,
+		});
+		
+		this.messageQueueTask = ProcessQueue();
+	}
+	
+	public bool TrySend<TMessage>(TMessage message) where TMessage : TMessageBase {
+		return messageQueue.Writer.TryWrite(PrepareMessage(message));
+	}
+	
+	public async ValueTask Send<TMessage>(TMessage message, CancellationToken cancellationToken = default) where TMessage : TMessageBase {
+		await messageQueue.Writer.WriteAsync(PrepareMessage(message), cancellationToken);
+	}
+	
+	public async Task<TReply> Send<TMessage, TReply>(TMessage message, TimeSpan waitForReplyTime, CancellationToken cancellationToken) where TMessage : TMessageBase, ICanReply<TReply> {
+		var preparedMessage = PrepareMessage(message);
+		var messageId = preparedMessage.MessageId;
+		
+		messageReplyTracker.RegisterReply(messageId);
+		try {
+			await messageQueue.Writer.WriteAsync(preparedMessage, cancellationToken);
+		} catch (Exception) {
+			messageReplyTracker.ForgetReply(messageId);
+			throw;
+		}
+		
+		return await messageReplyTracker.WaitForReply<TReply>(messageId, waitForReplyTime, cancellationToken);
+	}
+	
+	private PreparedMessage PrepareMessage(TMessageBase message) {
+		uint messageId = Interlocked.Increment(ref nextMessageId);
+		return new PreparedMessage(messageId, message);
+	}
+	
+	private readonly record struct PreparedMessage(uint MessageId, TMessageBase Message);
+	
+	private async Task ProcessQueue() {
+		CancellationToken cancellationToken = shutdownCancellationTokenSource.Token;
+		Queue<PreparedMessage> messagesInTransit = new (capacity: 10);
+		
+		while (await messageQueue.Reader.WaitToReadAsync(cancellationToken)) {
+			do {
+				while (messagesInTransit.Count < messagesInTransit.Capacity) {
+					if (messageQueue.Reader.TryRead(out var nextMessage)) {
+						messagesInTransit.Enqueue(nextMessage);
+					}
+					else {
+						break;
+					}
+				}
+				
+				RpcFrameSender<TMessageBase> frameSender;
+				
+				foreach ((uint messageId, TMessageBase message) in messagesInTransit) {
+					await frameSender.SendFrame(messageRegistry.CreateFrame(messageId, message), cancellationToken);
+				}
+			} while (messagesInTransit.Count > 0);
+		}
+	}
+	
+	internal void ReceiveAcknowledgment(AcknowledgmentFrame frame) {
+		// TODO wait for reply instead?
+	}
+	
+	internal void ReceiveReply(ReplyFrame frame) {
+		messageReplyTracker.ReceiveReply(frame.ReplyingToMessageId, frame.SerializedReply);
+	}
+	
+	internal void ReceiveError(ErrorFrame frame) {
+		messageReplyTracker.FailReply(frame.ReplyingToMessageId, RpcErrorException.From(frame.Error));
+	}
+	
+	internal async Task Close() {
+		messageQueue.Writer.TryComplete();
+		
+		try {
+			await messageQueueTask.WaitAsync(TimeSpan.FromSeconds(15));
+		} catch (TimeoutException) {
+			logger.Warning("Could not finish processing message queue before timeout, forcibly shutting it down.");
+			await shutdownCancellationTokenSource.CancelAsync();
+		} catch (Exception) {
+			// Ignore.
+		}
+		
+		messageQueueTask.Dispose();
+		shutdownCancellationTokenSource.Dispose();
+	}
+}

Utils/Phantom.Utils.Rpc/Runtime/Client/RpcClient.cs

@@ -11,29 +11,21 @@ public sealed class RpcClient<TClientToServerMessage, TServerToClientMessage> :
 		return connection == null ? null : new RpcClient<TClientToServerMessage, TServerToClientMessage>(loggerName, connectionParameters, messageDefinitions, connector, connection);
 	}
 	
-	private readonly string loggerName;
 	private readonly ILogger logger;
-	private readonly MessageRegistry<TServerToClientMessage> messageRegistry;
-	private readonly MessageReceiveTracker messageReceiveTracker = new ();
-	private readonly RpcClientToServerConnection connection;
+	private readonly RpcClientToServerConnection<TClientToServerMessage, TServerToClientMessage> connection;
 	private readonly CancellationTokenSource shutdownCancellationTokenSource = new ();
 	
-	public RpcSendChannel<TClientToServerMessage> SendChannel { get; }
+	public MessageSender<TClientToServerMessage> MessageSender { get; }
 	
 	private RpcClient(string loggerName, RpcClientConnectionParameters connectionParameters, IMessageDefinitions<TClientToServerMessage, TServerToClientMessage> messageDefinitions, RpcClientToServerConnector connector, RpcClientToServerConnector.Connection connection) {
-		this.loggerName = loggerName;
 		this.logger = PhantomLogger.Create<RpcClient<TClientToServerMessage, TServerToClientMessage>>(loggerName);
-		this.messageRegistry = messageDefinitions.ToClient;
-		
-		this.connection = new RpcClientToServerConnection(loggerName, connector, connection);
-		this.SendChannel = new RpcSendChannel<TClientToServerMessage>(loggerName, connectionParameters.Common, this.connection, messageDefinitions.ToServer);
+		this.connection = new RpcClientToServerConnection<TClientToServerMessage, TServerToClientMessage>(loggerName, messageDefinitions.ToClient, connectionParameters.Common, connector, connection);
+		this.MessageSender = new MessageSender<TClientToServerMessage>(loggerName, messageDefinitions.ToServer, connectionParameters.Common);
 	}
 	
-	public async Task Listen(IMessageReceiver<TServerToClientMessage> receiver) {
-		var messageHandler = new RpcMessageHandler<TServerToClientMessage>(receiver, SendChannel);
-		var frameReader = new RpcFrameReader<TClientToServerMessage, TServerToClientMessage>(loggerName, messageRegistry, messageReceiveTracker, messageHandler, SendChannel);
+	public async Task Listen(IMessageReceiver<TServerToClientMessage> messageReceiver) {
 		try {
-			await connection.ReadConnection(frameReader, shutdownCancellationTokenSource.Token);
+			await connection.ReadConnection(MessageSender, messageReceiver, shutdownCancellationTokenSource.Token);
 		} catch (OperationCanceledException) {
 			// Ignore.
 		}
@@ -43,9 +35,9 @@ public sealed class RpcClient<TClientToServerMessage, TServerToClientMessage> :
 		logger.Information("Shutting down client...");
 		
 		try {
-			await SendChannel.Close();
+			await MessageSender.Close();
 		} catch (Exception e) {
-			logger.Error(e, "Caught exception while closing send channel.");
+			logger.Error(e, "Caught exception while closing message sender.");
 		}
 		
 		try {
@@ -61,6 +53,5 @@ public sealed class RpcClient<TClientToServerMessage, TServerToClientMessage> :
 	
 	public void Dispose() {
 		connection.Dispose();
-		SendChannel.Dispose();
 	}
 }

Utils/Phantom.Utils.Rpc/Runtime/Client/RpcClientConnectionParameters.cs

@@ -3,15 +3,12 @@ using Phantom.Utils.Rpc.Runtime.Tls;
 
 namespace Phantom.Utils.Rpc.Runtime.Client;
 
-public readonly record struct RpcClientConnectionParameters(
+public sealed record RpcClientConnectionParameters(
 	string Host,
 	ushort Port,
 	string DistinguishedName,
 	RpcCertificateThumbprint CertificateThumbprint,
 	AuthToken AuthToken,
 	IRpcClientHandshake Handshake,
-	ushort SendQueueCapacity,
-	TimeSpan PingInterval
-) {
-	internal RpcCommonConnectionParameters Common => new (SendQueueCapacity, PingInterval);
-}
+	RpcCommonConnectionParameters CommonParameters
+);

Utils/Phantom.Utils.Rpc/Runtime/Client/RpcClientToServerConnection.cs

@@ -1,12 +1,19 @@
 using System.Net.Sockets;
 using Phantom.Utils.Logging;
 using Phantom.Utils.Rpc.Frame;
+using Phantom.Utils.Rpc.Message;
 using Serilog;
 
 namespace Phantom.Utils.Rpc.Runtime.Client;
 
-sealed class RpcClientToServerConnection(string loggerName, RpcClientToServerConnector connector, RpcClientToServerConnector.Connection initialConnection) : IRpcConnectionProvider, IDisposable {
-	private readonly ILogger logger = PhantomLogger.Create<RpcClientToServerConnection>(loggerName);
+sealed class RpcClientToServerConnection<TClientToServerMessage, TServerToClientMessage>(
+	string loggerName,
+	MessageRegistry<TServerToClientMessage> messageRegistry,
+	RpcCommonConnectionParameters connectionParameters,
+	RpcClientToServerConnector connector,
+	RpcClientToServerConnector.Connection initialConnection
+) : IRpcConnectionProvider, IDisposable {
+	private readonly ILogger logger = PhantomLogger.Create<RpcClientToServerConnection<TClientToServerMessage, TServerToClientMessage>>(loggerName);
 	
 	private readonly SemaphoreSlim semaphore = new (1);
 	private RpcClientToServerConnector.Connection currentConnection = initialConnection;
@@ -30,9 +37,11 @@ sealed class RpcClientToServerConnection(string loggerName, RpcClientToServerCon
 		}
 	}
 	
-	public async Task ReadConnection(IFrameReader frameReader, CancellationToken cancellationToken) {
+	public async Task ReadConnection(MessageSender<TClientToServerMessage> messageSender, IMessageReceiver<TServerToClientMessage> messageReceiver, CancellationToken cancellationToken) {
 		RpcClientToServerConnector.Connection? connection = null;
 		
+		var sessionState = NewSessionState(messageSender, messageReceiver);
+		
 		try {
 			while (true) {
 				connection?.Dispose();
@@ -47,8 +56,13 @@ sealed class RpcClientToServerConnection(string loggerName, RpcClientToServerCon
 					continue;
 				}
 				
+				if (connection.RestartSession) {
+					await sessionState.FrameSender.ShutdownNow();
+					sessionState = NewSessionState(messageSender, messageReceiver);
+				}
+				
 				try {
-					await IFrame.ReadFrom(connection.Stream, frameReader, cancellationToken);
+					await IFrame.ReadFrom(connection.Stream, sessionState.FrameReader, cancellationToken);
 				} catch (OperationCanceledException) {
 					throw;
 				} catch (EndOfStreamException) {
@@ -66,6 +80,12 @@ sealed class RpcClientToServerConnection(string loggerName, RpcClientToServerCon
 				}
 			}
 		} finally {
+			try {
+				await sessionState.FrameSender.Shutdown();
+			} catch (Exception e) {
+				logger.Error(e, "Caught exception while closing frame sender.");
+			}
+			
 			if (connection != null) {
 				try {
 					await connection.Disconnect();
@@ -76,6 +96,15 @@ sealed class RpcClientToServerConnection(string loggerName, RpcClientToServerCon
 		}
 	}
 	
+	private SessionState NewSessionState(MessageSender<TClientToServerMessage> messageSender, IMessageReceiver<TServerToClientMessage> messageReceiver) {
+		var frameSender = new RpcFrameSender<TClientToServerMessage>(loggerName, connectionParameters, this);
+		var messageHandler = new MessageHandler<TServerToClientMessage>(messageReceiver, frameSender);
+		var frameReader = new RpcFrameReader<TClientToServerMessage, TServerToClientMessage>(loggerName, connectionParameters, messageRegistry, messageHandler, messageSender, frameSender);
+		return new SessionState(frameSender, frameReader);
+	}
+	
+	private readonly record struct SessionState(RpcFrameSender<TClientToServerMessage> FrameSender, RpcFrameReader<TClientToServerMessage, TServerToClientMessage> FrameReader);
+	
 	public void StopReconnecting() {
 		newConnectionCancellationTokenSource.Cancel();
 	}

Utils/Phantom.Utils.Rpc/Runtime/Client/RpcClientToServerConnector.cs

@@ -4,12 +4,13 @@ using System.Security.Authentication;
 using System.Security.Cryptography.X509Certificates;
 using Phantom.Utils.Collections;
 using Phantom.Utils.Logging;
+using Phantom.Utils.Rpc.Handshake;
 using Phantom.Utils.Rpc.Runtime.Tls;
 using Serilog;
 
 namespace Phantom.Utils.Rpc.Runtime.Client;
 
-internal sealed class RpcClientToServerConnector {
+sealed class RpcClientToServerConnector {
 	private static readonly TimeSpan InitialRetryDelay = TimeSpan.FromMilliseconds(100);
 	private static readonly TimeSpan MaximumRetryDelay = TimeSpan.FromSeconds(30);
 	private static readonly TimeSpan DisconnectTimeout = TimeSpan.FromSeconds(10);
@@ -112,9 +113,10 @@ internal sealed class RpcClientToServerConnector {
 		try {
 			stream = new SslStream(new NetworkStream(clientSocket, ownsSocket: false), leaveInnerStreamOpen: false);
 			
-			if (await FinalizeConnection(stream, cancellationToken)) {
+			var handshakeResult = await FinalizeConnection(stream, cancellationToken);
+			if (handshakeResult != RpcFinalHandshakeResult.Error) {
 				logger.Information("Connected to {Host}:{Port}.", parameters.Host, parameters.Port);
-				return new Connection(clientSocket, stream);
+				return new Connection(clientSocket, stream, RestartSession: handshakeResult == RpcFinalHandshakeResult.NewSession);
 			}
 		} catch (Exception e) {
 			logger.Error(e, "Caught unhandled exception.");
@@ -130,7 +132,7 @@ internal sealed class RpcClientToServerConnector {
 		return null;
 	}
 	
-	private async Task<bool> FinalizeConnection(SslStream stream, CancellationToken cancellationToken) {
+	private async Task<RpcFinalHandshakeResult> FinalizeConnection(SslStream stream, CancellationToken cancellationToken) {
 		try {
 			loggedCertificateValidationError = false;
 			await stream.AuthenticateAsClientAsync(sslOptions, cancellationToken);
@@ -139,7 +141,7 @@ internal sealed class RpcClientToServerConnector {
 				logger.Error(e, "Could not establish a secure connection.");
 			}
 			
-			return false;
+			return RpcFinalHandshakeResult.Error;
 		}
 		
 		logger.Information("Established a secure connection.");
@@ -148,30 +150,31 @@ internal sealed class RpcClientToServerConnector {
 			return await PerformApplicationHandshake(stream, cancellationToken);
 		} catch (EndOfStreamException) {
 			logger.Warning("Could not perform application handshake, connection lost.");
-			return false;
+			return RpcFinalHandshakeResult.Error;
 		} catch (Exception e) {
 			logger.Warning(e, "Could not perform application handshake.");
-			return false;
+			return RpcFinalHandshakeResult.Error;
 		}
 	}
 	
-	private async Task<bool> PerformApplicationHandshake(Stream stream, CancellationToken cancellationToken) {
+	private async Task<RpcFinalHandshakeResult> PerformApplicationHandshake(Stream stream, CancellationToken cancellationToken) {
 		await RpcSerialization.WriteAuthToken(parameters.AuthToken, stream, cancellationToken);
 		
 		if (await RpcSerialization.ReadByte(stream, cancellationToken) != 1) {
 			logger.Error("Server rejected authorization token.");
-			return false;
+			return RpcFinalHandshakeResult.Error;
 		}
 		
 		await RpcSerialization.WriteGuid(sessionId, stream, cancellationToken);
 		await parameters.Handshake.Perform(stream, cancellationToken);
 		
-		if (await RpcSerialization.ReadByte(stream, cancellationToken) != 1) {
+		RpcFinalHandshakeResult finalHandshakeResult = (RpcFinalHandshakeResult) await RpcSerialization.ReadByte(stream, cancellationToken);
+		
+		if (finalHandshakeResult == RpcFinalHandshakeResult.Error) {
 			logger.Error("Server rejected client due to unknown error.");
-			return false;
 		}
 		
-		return true;
+		return finalHandshakeResult;
 	}
 	
 	private bool ValidateServerCertificate(object sender, X509Certificate? certificate, X509Chain? chain, SslPolicyErrors sslPolicyErrors) {
@@ -207,7 +210,7 @@ internal sealed class RpcClientToServerConnector {
 		await socket.DisconnectAsync(reuseSocket: false, timeoutTokenSource.Token);
 	}
 	
-	internal sealed record Connection(Socket Socket, Stream Stream) : IDisposable {
+	internal sealed record Connection(Socket Socket, Stream Stream, bool RestartSession) : IDisposable {
 		public async Task Disconnect() {
 			await DisconnectSocket(Socket, Stream);
 		}

Utils/Phantom.Utils.Rpc/Runtime/RpcCommonConnectionParameters.cs

@@ -1,6 +1,8 @@
 namespace Phantom.Utils.Rpc.Runtime;
 
-readonly record struct RpcCommonConnectionParameters(
-	ushort SendQueueCapacity,
+public sealed record RpcCommonConnectionParameters(
+	ushort MessageQueueCapacity,
+	ushort FrameQueueCapacity,
+	ushort MaxConcurrentlyHandledMessages,
 	TimeSpan PingInterval
 );

Utils/Phantom.Utils.Rpc/Runtime/RpcError.cs

@@ -6,5 +6,6 @@ enum RpcError : byte {
 	MessageTooLarge = 2,
 	MessageDeserializationError = 3,
 	MessageHandlingError = 4,
-	MessageAlreadyHandled = 5,
+	MessageReplyingError = 5,
+	ReplyTooLarge = 6,
 }

Utils/Phantom.Utils.Rpc/Runtime/RpcErrorException.cs

@@ -3,13 +3,14 @@
 sealed class RpcErrorException : Exception {
 	internal static RpcErrorException From(RpcError error) {
 		return error switch {
-			RpcError.InvalidData                 => new RpcErrorException("Invalid data", error),
-			RpcError.UnknownMessageRegistryCode  => new RpcErrorException("Unknown message registry code", error),
-			RpcError.MessageTooLarge             => new RpcErrorException("Message is too large", error),
-			RpcError.MessageDeserializationError => new RpcErrorException("Message deserialization error", error),
-			RpcError.MessageHandlingError        => new RpcErrorException("Message handling error", error),
-			RpcError.MessageAlreadyHandled       => new RpcErrorException("Message already handled", error),
-			_                                    => new RpcErrorException("Unknown error", error),
+			RpcError.InvalidData                 => new RpcErrorException("Invalid data.", error),
+			RpcError.UnknownMessageRegistryCode  => new RpcErrorException("Unknown message registry code.", error),
+			RpcError.MessageTooLarge             => new RpcErrorException("Message is too large.", error),
+			RpcError.MessageDeserializationError => new RpcErrorException("Message deserialization error.", error),
+			RpcError.MessageHandlingError        => new RpcErrorException("Message handling error.", error),
+			RpcError.MessageReplyingError        => new RpcErrorException("Message replying error.", error),
+			RpcError.ReplyTooLarge               => new RpcErrorException("Reply is too large.", error),
+			_                                    => new RpcErrorException("Unknown error.", error),
 		};
 	}
 	

Utils/Phantom.Utils.Rpc/Runtime/RpcFrameReader.cs

@@ -8,43 +8,71 @@ namespace Phantom.Utils.Rpc.Runtime;
 
 sealed class RpcFrameReader<TSentMessage, TReceivedMessage>(
 	string loggerName,
+	RpcCommonConnectionParameters connectionParameters,
 	MessageRegistry<TReceivedMessage> messageRegistry,
-	MessageReceiveTracker messageReceiveTracker,
-	RpcMessageHandler<TReceivedMessage> messageHandler,
-	RpcSendChannel<TSentMessage> sendChannel
+	MessageHandler<TReceivedMessage> messageHandler,
+	MessageSender<TSentMessage> messageSender,
+	RpcFrameSender<TSentMessage> frameSender
 ) : IFrameReader {
 	private readonly ILogger logger = PhantomLogger.Create<RpcFrameReader<TSentMessage, TReceivedMessage>>(loggerName);
 	
+	private readonly ushort maxConcurrentlyHandledMessages = connectionParameters.MaxConcurrentlyHandledMessages;
+	private readonly SemaphoreSlim messageHandlingSemaphore = new (connectionParameters.MaxConcurrentlyHandledMessages);
+	
 	public ValueTask OnPingFrame(DateTimeOffset pingTime, CancellationToken cancellationToken) {
 		messageHandler.OnPing();
-		return sendChannel.SendPong(pingTime, cancellationToken);
+		return frameSender.SendPong(pingTime, cancellationToken);
 	}
 	
 	public void OnPongFrame(PongFrame frame) {
-		sendChannel.ReceivePong(frame);
+		frameSender.ReceivePong(frame);
 	}
 	
-	public Task OnMessageFrame(MessageFrame frame, CancellationToken cancellationToken) {
-		if (!messageReceiveTracker.ReceiveMessage(frame.MessageId)) {
+	public async Task OnMessageFrame(MessageFrame frame, CancellationToken cancellationToken) {
+		if (!frameSender.ReceiveMessage(frame)) {
 			logger.Warning("Received duplicate message {MessageId}.", frame.MessageId);
-			return messageHandler.SendError(frame.MessageId, RpcError.MessageAlreadyHandled, cancellationToken).AsTask();
+			return;
 		}
 		
 		if (messageRegistry.TryGetType(frame, out var messageType)) {
 			logger.Verbose("Received message {MesageId} of type {MessageType} ({Bytes} B).", frame.MessageId, messageType.Name, frame.SerializedMessage.Length);
 		}
 		
-		return messageRegistry.Handle(frame, messageHandler, cancellationToken);
+		Task acquireSemaphore = messageHandlingSemaphore.WaitAsync(cancellationToken);
+		try {
+			if (!acquireSemaphore.IsCompleted) {
+				logger.Warning("Reached limit for concurrently handled messages ({Limit}).", maxConcurrentlyHandledMessages);
+			}
+			
+			await acquireSemaphore;
+			_ = HandleMessage(frame, cancellationToken);
+		} catch (Exception) {
+			messageHandlingSemaphore.Release();
+			throw;
+		}
+	}
+	
+	private async Task HandleMessage(MessageFrame frame, CancellationToken cancellationToken) {
+		try {
+			await messageRegistry.Handle(frame, messageHandler, cancellationToken);
+		} finally {
+			messageHandlingSemaphore.Release();
+		}
+	}
+	
+	public void OnAcknowledgmentFrame(AcknowledgmentFrame frame) {
+		logger.Verbose("Received acknowledgment of messages {FirstMessageId}-{LastMessageId}.", frame.FirstMessageId, frame.LastMessageId);
+		messageSender.ReceiveAcknowledgment(frame);
 	}
 	
 	public void OnReplyFrame(ReplyFrame frame) {
 		logger.Verbose("Received reply to message {MesageId} ({Bytes} B).", frame.ReplyingToMessageId, frame.SerializedReply.Length);
-		sendChannel.ReceiveReply(frame);
+		messageSender.ReceiveReply(frame);
 	}
 	
 	public void OnErrorFrame(ErrorFrame frame) {
 		logger.Warning("Received error response to message {MesageId}: {Error}", frame.ReplyingToMessageId, frame.Error);
-		sendChannel.ReceiveError(frame.ReplyingToMessageId, frame.Error);
+		messageSender.ReceiveError(frame);
 	}
 	
 	public void OnUnknownFrameId(byte frameId) {

Utils/Phantom.Utils.Rpc/Runtime/RpcFrameSender.cs

@@ -0,0 +1,176 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Threading.Channels;
+using Phantom.Utils.Logging;
+using Phantom.Utils.Rpc.Frame;
+using Phantom.Utils.Rpc.Frame.Types;
+using Phantom.Utils.Rpc.Message;
+using Serilog;
+
+namespace Phantom.Utils.Rpc.Runtime;
+
+sealed class RpcFrameSender<TMessageBase> : IMessageReplySender {
+	private readonly ILogger logger;
+	private readonly IRpcConnectionProvider connectionProvider;
+	private readonly MessageReceiveTracker messageReceiveTracker = new ();
+	private readonly MessageAcknowledgmentQueue acknowledgmentQueue = new ();
+	
+	private readonly Channel<IFrame> frameQueue;
+	private readonly Task frameQueueTask;
+	private readonly Task pingTask;
+	private readonly Task acknowledgementTask;
+	
+	private readonly CancellationTokenSource sendQueueCancellationTokenSource = new ();
+	private readonly CancellationTokenSource pingCancellationTokenSource = new ();
+	private readonly CancellationTokenSource acknowledgementCancellationTokenSource = new ();
+	
+	private TaskCompletionSource<DateTimeOffset>? pongTask;
+	
+	internal RpcFrameSender(string loggerName, RpcCommonConnectionParameters connectionParameters, IRpcConnectionProvider connectionProvider) {
+		this.logger = PhantomLogger.Create<RpcFrameSender<TMessageBase>>(loggerName);
+		this.connectionProvider = connectionProvider;
+		
+		this.frameQueue = Channel.CreateBounded<IFrame>(new BoundedChannelOptions(connectionParameters.FrameQueueCapacity) {
+			AllowSynchronousContinuations = false,
+			FullMode = BoundedChannelFullMode.Wait,
+			SingleReader = true,
+			SingleWriter = false,
+		});
+		
+		this.frameQueueTask = ProcessQueue();
+		this.pingTask = PingSchedule(connectionParameters.PingInterval);
+		this.acknowledgementTask = AcknowledgementSchedule();
+	}
+	
+	public async ValueTask SendPong(DateTimeOffset pingTime, CancellationToken cancellationToken) {
+		await SendFrame(new PongFrame(pingTime), cancellationToken);
+	}
+	
+	async ValueTask IMessageReplySender.SendEmptyReply(uint replyingToMessageId, CancellationToken cancellationToken) {
+		await SendFrame(new ReplyFrame(replyingToMessageId, ReadOnlyMemory<byte>.Empty), cancellationToken);
+	}
+	
+	async ValueTask IMessageReplySender.SendReply<TReply>(uint replyingToMessageId, TReply reply, CancellationToken cancellationToken) {
+		await SendFrame(new ReplyFrame(replyingToMessageId, RpcSerialization.Serialize(reply)), cancellationToken);
+	}
+	
+	async ValueTask IMessageReplySender.SendError(uint replyingToMessageId, RpcError error, CancellationToken cancellationToken) {
+		await SendFrame(new ErrorFrame(replyingToMessageId, error), cancellationToken);
+	}
+	
+	public async ValueTask SendFrame(IFrame frame, CancellationToken cancellationToken) {
+		if (!frameQueue.Writer.TryWrite(frame)) {
+			logger.Warning("Send queue is full!");
+			await frameQueue.Writer.WriteAsync(frame, cancellationToken);
+		}
+	}
+	
+	private async Task ProcessQueue() {
+		CancellationToken cancellationToken = sendQueueCancellationTokenSource.Token;
+		
+		await foreach (IFrame frame in frameQueue.Reader.ReadAllAsync(cancellationToken)) {
+			while (true) {
+				try {
+					Stream stream = await connectionProvider.GetStream(cancellationToken);
+					await stream.WriteAsync(frame.FrameType, cancellationToken);
+					await frame.Write(stream, cancellationToken);
+					await stream.FlushAsync(cancellationToken);
+					break;
+				} catch (OperationCanceledException) {
+					throw;
+				} catch (Exception) {
+					// Retry.
+				}
+			}
+		}
+	}
+	
+	[SuppressMessage("ReSharper", "FunctionNeverReturns")]
+	private async Task PingSchedule(TimeSpan interval) {
+		CancellationToken cancellationToken = pingCancellationTokenSource.Token;
+		
+		while (true) {
+			await Task.Delay(interval, cancellationToken);
+			
+			pongTask = new TaskCompletionSource<DateTimeOffset>();
+			
+			if (!frameQueue.Writer.TryWrite(PingFrame.Instance)) {
+				cancellationToken.ThrowIfCancellationRequested();
+				logger.Warning("Skipped a ping due to a full queue.");
+				continue;
+			}
+			
+			DateTimeOffset pingTime = await pongTask.Task.WaitAsync(cancellationToken);
+			DateTimeOffset currentTime = DateTimeOffset.UtcNow;
+			
+			TimeSpan roundTripTime = currentTime - pingTime;
+			logger.Information("Received pong, round trip time: {RoundTripTime} ms", (long) roundTripTime.TotalMilliseconds);
+		}
+	}
+	
+	[SuppressMessage("ReSharper", "FunctionNeverReturns")]
+	private async Task AcknowledgementSchedule() {
+		CancellationToken cancellationToken = acknowledgementCancellationTokenSource.Token;
+		TimeSpan interval = TimeSpan.FromSeconds(1);
+		
+		while (true) {
+			await acknowledgmentQueue.Wait(cancellationToken);
+			await Task.Delay(interval, cancellationToken);
+			
+			foreach (var acknowledgmentFrame in acknowledgmentQueue.Drain()) {
+				await SendFrame(acknowledgmentFrame, cancellationToken);
+			}
+		}
+	}
+	
+	public bool ReceiveMessage(MessageFrame frame) {
+		acknowledgmentQueue.Enqueue(frame.MessageId);
+		return messageReceiveTracker.ReceiveMessage(frame.MessageId);
+	}
+	
+	public void ReceivePong(PongFrame frame) {
+		pongTask?.TrySetResult(frame.PingTime);
+	}
+	
+	public async Task Shutdown() {
+		await pingCancellationTokenSource.CancelAsync();
+		await acknowledgementCancellationTokenSource.CancelAsync();
+		frameQueue.Writer.TryComplete();
+		
+		await pingTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+		await acknowledgementTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+		
+		try {
+			await frameQueueTask.WaitAsync(TimeSpan.FromSeconds(15));
+		} catch (TimeoutException) {
+			logger.Warning("Could not finish processing frame queue before timeout, forcibly shutting it down.");
+			await sendQueueCancellationTokenSource.CancelAsync();
+		} catch (Exception) {
+			// Ignore.
+		}
+		
+		Dispose();
+	}
+	
+	public async Task ShutdownNow() {
+		await pingCancellationTokenSource.CancelAsync();
+		await acknowledgementCancellationTokenSource.CancelAsync();
+		await sendQueueCancellationTokenSource.CancelAsync();
+		frameQueue.Writer.TryComplete();
+		
+		await pingTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+		await acknowledgementTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+		await frameQueueTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
+		
+		Dispose();
+	}
+	
+	private void Dispose() {
+		frameQueueTask.Dispose();
+		pingTask.Dispose();
+		acknowledgementTask.Dispose();
+		
+		sendQueueCancellationTokenSource.Dispose();
+		pingCancellationTokenSource.Dispose();
+		acknowledgementCancellationTokenSource.Dispose();
+	}
+}

Utils/Phantom.Utils.Rpc/Runtime/RpcMessageHandler.cs

@@ -1,19 +0,0 @@
-using Phantom.Utils.Rpc.Message;
-
-namespace Phantom.Utils.Rpc.Runtime;
-
-sealed class RpcMessageHandler<TMessageBase>(IMessageReceiver<TMessageBase> receiver, IRpcReplySender replySender) {
-	public IMessageReceiver<TMessageBase> Receiver => receiver;
-	
-	public void OnPing() {
-		receiver.OnPing();
-	}
-	
-	public ValueTask SendReply<TReply>(uint messageId, TReply reply, CancellationToken cancellationToken) {
-		return replySender.SendReply(messageId, reply, cancellationToken);
-	}
-	
-	public ValueTask SendError(uint messageId, RpcError error, CancellationToken cancellationToken) {
-		return replySender.SendError(messageId, error, cancellationToken);
-	}
-}

Utils/Phantom.Utils.Rpc/Runtime/RpcSendChannel.cs

@@ -1,168 +0,0 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Threading.Channels;
-using Phantom.Utils.Actor;
-using Phantom.Utils.Logging;
-using Phantom.Utils.Rpc.Frame;
-using Phantom.Utils.Rpc.Frame.Types;
-using Phantom.Utils.Rpc.Message;
-using Serilog;
-
-namespace Phantom.Utils.Rpc.Runtime;
-
-public sealed class RpcSendChannel<TMessageBase> : IRpcReplySender, IDisposable {
-	private readonly ILogger logger;
-	private readonly IRpcConnectionProvider connectionProvider;
-	private readonly MessageRegistry<TMessageBase> messageRegistry;
-	private readonly MessageReplyTracker messageReplyTracker;
-	
-	private readonly Channel<IFrame> sendQueue;
-	private readonly Task sendQueueTask;
-	private readonly Task pingTask;
-	
-	private readonly CancellationTokenSource sendQueueCancellationTokenSource = new ();
-	private readonly CancellationTokenSource pingCancellationTokenSource = new ();
-	
-	private uint nextMessageId;
-	private TaskCompletionSource<DateTimeOffset>? pongTask;
-	
-	internal RpcSendChannel(string loggerName, RpcCommonConnectionParameters connectionParameters, IRpcConnectionProvider connectionProvider, MessageRegistry<TMessageBase> messageRegistry) {
-		this.logger = PhantomLogger.Create<RpcSendChannel<TMessageBase>>(loggerName);
-		this.connectionProvider = connectionProvider;
-		this.messageRegistry = messageRegistry;
-		this.messageReplyTracker = new MessageReplyTracker(loggerName);
-		
-		this.sendQueue = Channel.CreateBounded<IFrame>(new BoundedChannelOptions(connectionParameters.SendQueueCapacity) {
-			AllowSynchronousContinuations = false,
-			FullMode = BoundedChannelFullMode.Wait,
-			SingleReader = true,
-			SingleWriter = false,
-		});
-		
-		this.sendQueueTask = ProcessSendQueue();
-		this.pingTask = Ping(connectionParameters.PingInterval);
-	}
-	
-	internal async ValueTask SendPong(DateTimeOffset pingTime, CancellationToken cancellationToken) {
-		await SendFrame(new PongFrame(pingTime), cancellationToken);
-	}
-	
-	public bool TrySendMessage<TMessage>(TMessage message) where TMessage : TMessageBase {
-		return sendQueue.Writer.TryWrite(NextMessageFrame(message));
-	}
-	
-	public async ValueTask SendMessage<TMessage>(TMessage message, CancellationToken cancellationToken = default) where TMessage : TMessageBase {
-		await SendFrame(NextMessageFrame(message), cancellationToken);
-	}
-	
-	public async Task<TReply> SendMessage<TMessage, TReply>(TMessage message, TimeSpan waitForReplyTime, CancellationToken cancellationToken) where TMessage : TMessageBase, ICanReply<TReply> {
-		MessageFrame frame = NextMessageFrame(message);
-		uint messageId = frame.MessageId;
-		
-		messageReplyTracker.RegisterReply(messageId);
-		try {
-			await SendFrame(frame, cancellationToken);
-		} catch (Exception) {
-			messageReplyTracker.ForgetReply(messageId);
-			throw;
-		}
-		
-		return await messageReplyTracker.WaitForReply<TReply>(messageId, waitForReplyTime, cancellationToken);
-	}
-	
-	async ValueTask IRpcReplySender.SendReply<TReply>(uint replyingToMessageId, TReply reply, CancellationToken cancellationToken) {
-		await SendFrame(new ReplyFrame(replyingToMessageId, RpcSerialization.Serialize(reply)), cancellationToken);
-	}
-	
-	async ValueTask IRpcReplySender.SendError(uint replyingToMessageId, RpcError error, CancellationToken cancellationToken) {
-		await SendFrame(new ErrorFrame(replyingToMessageId, error), cancellationToken);
-	}
-	
-	private async ValueTask SendFrame(IFrame frame, CancellationToken cancellationToken) {
-		if (!sendQueue.Writer.TryWrite(frame)) {
-			logger.Warning("Send queue is full!");
-			await sendQueue.Writer.WriteAsync(frame, cancellationToken);
-		}
-	}
-	
-	private MessageFrame NextMessageFrame<TMessage>(TMessage message) where TMessage : TMessageBase {
-		uint messageId = Interlocked.Increment(ref nextMessageId);
-		return messageRegistry.CreateFrame(messageId, message);
-	}
-	
-	private async Task ProcessSendQueue() {
-		CancellationToken cancellationToken = sendQueueCancellationTokenSource.Token;
-		
-		await foreach (IFrame frame in sendQueue.Reader.ReadAllAsync(cancellationToken)) {
-			while (true) {
-				try {
-					Stream stream = await connectionProvider.GetStream(cancellationToken);
-					await stream.WriteAsync(frame.FrameType, cancellationToken);
-					await frame.Write(stream, cancellationToken);
-					await stream.FlushAsync(cancellationToken);
-					break;
-				} catch (OperationCanceledException) {
-					throw;
-				} catch (Exception) {
-					// Retry.
-				}
-			}
-		}
-	}
-	
-	[SuppressMessage("ReSharper", "FunctionNeverReturns")]
-	private async Task Ping(TimeSpan interval) {
-		CancellationToken cancellationToken = pingCancellationTokenSource.Token;
-		
-		while (true) {
-			await Task.Delay(interval, cancellationToken);
-			
-			pongTask = new TaskCompletionSource<DateTimeOffset>();
-			
-			if (!sendQueue.Writer.TryWrite(PingFrame.Instance)) {
-				cancellationToken.ThrowIfCancellationRequested();
-				logger.Warning("Skipped a ping due to a full queue.");
-				continue;
-			}
-			
-			DateTimeOffset pingTime = await pongTask.Task.WaitAsync(cancellationToken);
-			DateTimeOffset currentTime = DateTimeOffset.UtcNow;
-			
-			TimeSpan roundTripTime = currentTime - pingTime;
-			logger.Information("Received pong, round trip time: {RoundTripTime} ms", (long) roundTripTime.TotalMilliseconds);
-		}
-	}
-	
-	internal void ReceivePong(PongFrame frame) {
-		pongTask?.TrySetResult(frame.PingTime);
-	}
-	
-	internal void ReceiveReply(ReplyFrame frame) {
-		messageReplyTracker.ReceiveReply(frame.ReplyingToMessageId, frame.SerializedReply);
-	}
-	
-	internal void ReceiveError(uint messageId, RpcError error) {
-		messageReplyTracker.FailReply(messageId, RpcErrorException.From(error));
-	}
-	
-	internal async Task Close() {
-		await pingCancellationTokenSource.CancelAsync();
-		sendQueue.Writer.TryComplete();
-		
-		await pingTask.ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
-		
-		try {
-			await sendQueueTask.WaitAsync(TimeSpan.FromSeconds(15));
-		} catch (TimeoutException) {
-			logger.Warning("Could not finish processing send queue before timeout, forcibly shutting it down.");
-			await sendQueueCancellationTokenSource.CancelAsync();
-		} catch (Exception) {
-			// Ignore.
-		}
-	}
-	
-	public void Dispose() {
-		sendQueueTask.Dispose();
-		sendQueueCancellationTokenSource.Dispose();
-		pingCancellationTokenSource.Dispose();
-	}
-}

Utils/Phantom.Utils.Rpc/Runtime/RpcSerialization.cs

@@ -91,6 +91,12 @@ public static class RpcSerialization {
 		return buffer;
 	}
 	
+	public static async ValueTask<ReadOnlyMemory<byte>> ReadBytes(uint length, Stream stream, CancellationToken cancellationToken) {
+		Memory<byte> buffer = new byte[length];
+		await stream.ReadExactlyAsync(buffer, cancellationToken);
+		return buffer;
+	}
+	
 	public static ReadOnlyMemory<byte> Serialize<T>(T value) {
 		var buffer = new ArrayBufferWriter<byte>();
 		MemoryPackSerializer.Serialize(buffer, value, SerializerOptions);

Utils/Phantom.Utils.Rpc/Runtime/Server/RpcServer.cs

@@ -25,7 +25,7 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 	public async Task<bool> Run(CancellationToken shutdownToken) {
 		EndPoint endPoint = connectionParameters.EndPoint;
 		
-		SslServerAuthenticationOptions sslOptions = new () {
+		var sslOptions = new SslServerAuthenticationOptions {
 			AllowRenegotiation = false,
 			AllowTlsResume = true,
 			CertificateRevocationCheckMode = X509RevocationMode.NoCheck,
@@ -35,6 +35,15 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 			ServerCertificate = connectionParameters.Certificate.Certificate,
 		};
 		
+		var serverData = new SharedData(
+			connectionParameters.Common,
+			connectionParameters.AuthToken,
+			messageDefinitions.ToServer,
+			clientHandshake,
+			clientRegistrar,
+			clientSessions
+		);
+		
 		try {
 			using var serverSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
 			
@@ -51,7 +60,7 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 				
 				while (true) {
 					Socket clientSocket = await serverSocket.AcceptAsync(shutdownToken);
-					clients.Add(new Client(loggerName, messageDefinitions, clientHandshake, clientRegistrar, clientSessions, clientSocket, sslOptions, connectionParameters.AuthToken, shutdownToken));
+					clients.Add(new Client(loggerName, serverData, clientSocket, sslOptions, shutdownToken));
 					clients.RemoveAll(static client => client.Task.IsCompleted);
 				}
 			} catch (OperationCanceledException) {
@@ -83,6 +92,15 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 		logger.Information("Server stopped.");
 	}
 	
+	private readonly record struct SharedData(
+		RpcCommonConnectionParameters ConnectionParameters,
+		AuthToken AuthToken,
+		MessageRegistry<TClientToServerMessage> MessageRegistry,
+		IRpcServerClientHandshake<THandshakeResult> ClientHandshake,
+		IRpcServerClientRegistrar<TClientToServerMessage, TServerToClientMessage, THandshakeResult> ClientRegistrar,
+		RpcServerClientSessions<TServerToClientMessage> ClientSessions
+	);
+	
 	private sealed class Client {
 		private static TimeSpan DisconnectTimeout => TimeSpan.FromSeconds(10);
 		
@@ -99,34 +117,22 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 		public Task Task { get; }
 		
 		private ILogger logger;
-		private readonly IMessageDefinitions<TClientToServerMessage, TServerToClientMessage> messageDefinitions;
-		private readonly IRpcServerClientHandshake<THandshakeResult> clientHandshake;
-		private readonly IRpcServerClientRegistrar<TClientToServerMessage, TServerToClientMessage, THandshakeResult> clientRegistrar;
-		private readonly RpcServerClientSessions<TServerToClientMessage> clientSessions;
+		private readonly SharedData sharedData;
 		private readonly Socket socket;
 		private readonly SslServerAuthenticationOptions sslOptions;
-		private readonly AuthToken authToken;
 		private readonly CancellationToken shutdownToken;
 		
 		public Client(
 			string serverLoggerName,
-			IMessageDefinitions<TClientToServerMessage, TServerToClientMessage> messageDefinitions,
-			IRpcServerClientHandshake<THandshakeResult> clientHandshake,
-			IRpcServerClientRegistrar<TClientToServerMessage, TServerToClientMessage, THandshakeResult> clientRegistrar,
-			RpcServerClientSessions<TServerToClientMessage> clientSessions,
+			SharedData sharedData,
 			Socket socket,
 			SslServerAuthenticationOptions sslOptions,
-			AuthToken authToken,
 			CancellationToken shutdownToken
 		) {
 			this.logger = PhantomLogger.Create<RpcServer<TClientToServerMessage, TServerToClientMessage, THandshakeResult>, Client>(PhantomLogger.ConcatNames(serverLoggerName, GetAddressDescriptor(socket)));
-			this.messageDefinitions = messageDefinitions;
-			this.clientHandshake = clientHandshake;
-			this.clientRegistrar = clientRegistrar;
-			this.clientSessions = clientSessions;
+			this.sharedData = sharedData;
 			this.socket = socket;
 			this.sslOptions = sslOptions;
-			this.authToken = authToken;
 			this.shutdownToken = shutdownToken;
 			
 			this.Task = Run();
@@ -207,7 +213,7 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 			
 			try {
 				var suppliedAuthToken = await RpcSerialization.ReadAuthToken(stream, cancellationToken);
-				if (!authToken.FixedTimeEquals(suppliedAuthToken)) {
+				if (!sharedData.AuthToken.FixedTimeEquals(suppliedAuthToken)) {
 					logger.Warning("Rejected client, invalid authorization token.");
 					await RpcSerialization.WriteByte(value: 0, stream, cancellationToken);
 					return null;
@@ -217,17 +223,17 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 				}
 				
 				var sessionId = await RpcSerialization.ReadGuid(stream, cancellationToken);
-				var session = clientSessions.GetOrCreateSession(sessionId);
+				var session = sharedData.ClientSessions.GetOrCreateSession(sessionId);
 				
-				logger.Information("Client connected with session {SessionId}, new logger name: {LoggerName}", sessionId, session.LoggerName);
+				logger.Information("Client connected with session {SessionId}, new logger name: {LoggerName}", session.SessionId, session.LoggerName);
 				logger = PhantomLogger.Create<RpcServer<TClientToServerMessage, TServerToClientMessage, THandshakeResult>, Client>(session.LoggerName);
 				
 				EstablishedConnection? establishedConnection;
-				switch (await clientHandshake.Perform(stream, cancellationToken)) {
+				switch (await sharedData.ClientHandshake.Perform(stream, cancellationToken)) {
 					case Left<THandshakeResult, Exception>(var handshakeResult):
 						try {
-							var connection = new RpcServerToClientConnection<TClientToServerMessage, TServerToClientMessage>(clientSessions, sessionId, messageDefinitions.ToServer, stream, session);
-							var messageReceiver = clientRegistrar.Register(connection, handshakeResult);
+							var connection = new RpcServerToClientConnection<TClientToServerMessage, TServerToClientMessage>(sharedData.ConnectionParameters, sharedData.MessageRegistry, sharedData.ClientSessions, session, stream);
+							var messageReceiver = sharedData.ClientRegistrar.Register(connection, handshakeResult);
 							
 							establishedConnection = new EstablishedConnection(session, connection, messageReceiver);
 						} catch (Exception e) {
@@ -247,14 +253,17 @@ public sealed class RpcServer<TClientToServerMessage, TServerToClientMessage, TH
 						break;
 				}
 				
+				RpcFinalHandshakeResult finalHandshakeResult;
 				if (establishedConnection == null) {
-					await RpcSerialization.WriteByte(value: 0, stream, cancellationToken);
-					return null;
+					finalHandshakeResult = RpcFinalHandshakeResult.Error;
 				}
 				else {
-					await RpcSerialization.WriteByte(value: 1, stream, cancellationToken);
-					return establishedConnection;
+					bool isNewSession = session.MarkFirstTimeUse();
+					finalHandshakeResult = isNewSession ? RpcFinalHandshakeResult.NewSession : RpcFinalHandshakeResult.ReusedSession;
 				}
+				
+				await RpcSerialization.WriteByte((byte) finalHandshakeResult, stream, cancellationToken);
+				return establishedConnection;
 			} catch (OperationCanceledException) {
 				throw;
 			} catch (EndOfStreamException) {

Utils/Phantom.Utils.Rpc/Runtime/Server/RpcServerClientSession.cs

@@ -1,18 +1,31 @@
-using Phantom.Utils.Rpc.Message;
+using Phantom.Utils.Logging;
+using Phantom.Utils.Rpc.Message;
+using Serilog;
 
 namespace Phantom.Utils.Rpc.Runtime.Server;
 
 sealed class RpcServerClientSession<TServerToClientMessage> : IRpcConnectionProvider {
-	public string LoggerName { get; }
-	public RpcSendChannel<TServerToClientMessage> SendChannel { get; }
-	public MessageReceiveTracker MessageReceiveTracker { get; }
+	private readonly ILogger logger;
 	
+	public string LoggerName { get; }
+	public Guid SessionId { get; }
+	public MessageSender<TServerToClientMessage> MessageSender { get; }
+	public RpcFrameSender<TServerToClientMessage> FrameSender { get; }
+	
+	private bool isNew = true;
 	private TaskCompletionSource<Stream> nextStream = new ();
 	
-	public RpcServerClientSession(string loggerName, RpcCommonConnectionParameters connectionParameters, MessageRegistry<TServerToClientMessage> messageRegistry) {
+	public RpcServerClientSession(string loggerName, Guid sessionId, RpcCommonConnectionParameters connectionParameters, MessageRegistry<TServerToClientMessage> messageRegistry) {
+		this.logger = PhantomLogger.Create<RpcServerClientSession<TServerToClientMessage>>(loggerName);
 		this.LoggerName = loggerName;
-		this.SendChannel = new RpcSendChannel<TServerToClientMessage>(loggerName, connectionParameters, this, messageRegistry);
-		this.MessageReceiveTracker = new MessageReceiveTracker();
+		this.SessionId = sessionId;
+		this.MessageSender = new MessageSender<TServerToClientMessage>(loggerName, messageRegistry, connectionParameters);
+		this.FrameSender = new RpcFrameSender<TServerToClientMessage>(loggerName, connectionParameters, this);
+	}
+	
+	/// <returns>Whether this was a new session. If it was a new session, it will be marked as used.</returns>
+	public bool MarkFirstTimeUse() {
+		return Interlocked.CompareExchange(ref isNew, value: true, comparand: false);
 	}
 	
 	public void OnConnected(Stream stream) {
@@ -39,7 +52,7 @@ sealed class RpcServerClientSession<TServerToClientMessage> : IRpcConnectionProv
 		}
 	}
 	
-	public Task Close() {
+	public async Task Close() {
 		lock (this) {
 			if (!nextStream.TrySetCanceled()) {
 				nextStream = new TaskCompletionSource<Stream>();
@@ -47,6 +60,16 @@ sealed class RpcServerClientSession<TServerToClientMessage> : IRpcConnectionProv
 			}
 		}
 		
-		return SendChannel.Close();
+		try {
+			await MessageSender.Close();
+		} catch (Exception e) {
+			logger.Error(e, "Caught exception while closing message sender.");
+		}
+		
+		try {
+			await FrameSender.Shutdown();
+		} catch (Exception e) {
+			logger.Error(e, "Caught exception while closing send channel.");
+		}
 	}
 }

Utils/Phantom.Utils.Rpc/Runtime/Server/RpcServerClientSessions.cs

@@ -29,7 +29,7 @@ sealed class RpcServerClientSessions<TServerToClientMessage> {
 	}
 	
 	private RpcServerClientSession<TServerToClientMessage> CreateSession(Guid sessionId, string loggerName) {
-		return new RpcServerClientSession<TServerToClientMessage>(loggerName, connectionParameters, messageRegistry);
+		return new RpcServerClientSession<TServerToClientMessage>(loggerName, sessionId, connectionParameters, messageRegistry);
 	}
 	
 	public Task CloseSession(Guid sessionId) {

Utils/Phantom.Utils.Rpc/Runtime/Server/RpcServerConnectionParameters.cs

@@ -4,12 +4,9 @@ using Phantom.Utils.Rpc.Runtime.Tls;
 
 namespace Phantom.Utils.Rpc.Runtime.Server;
 
-public readonly record struct RpcServerConnectionParameters(
+public sealed record RpcServerConnectionParameters(
 	EndPoint EndPoint,
 	RpcServerCertificate Certificate,
 	AuthToken AuthToken,
-	ushort SendQueueCapacity,
-	TimeSpan PingInterval
-) {
-	internal RpcCommonConnectionParameters Common => new (SendQueueCapacity, PingInterval);
-}
+	RpcCommonConnectionParameters CommonParameters
+);

Utils/Phantom.Utils.Rpc/Runtime/Server/RpcServerToClientConnection.cs

@@ -6,32 +6,29 @@ using Serilog;
 namespace Phantom.Utils.Rpc.Runtime.Server;
 
 public sealed class RpcServerToClientConnection<TClientToServerMessage, TServerToClientMessage> {
-	private readonly string loggerName;
 	private readonly ILogger logger;
-	private readonly RpcServerClientSessions<TServerToClientMessage> sessions;
+	private readonly RpcCommonConnectionParameters connectionParameters;
 	private readonly MessageRegistry<TClientToServerMessage> messageRegistry;
-	private readonly MessageReceiveTracker messageReceiveTracker;
+	private readonly RpcServerClientSessions<TServerToClientMessage> sessions;
+	private readonly RpcServerClientSession<TServerToClientMessage> session;
 	private readonly Stream stream;
 	private readonly CancellationTokenSource closeCancellationTokenSource = new ();
 	
-	public Guid SessionId { get; }
-	public RpcSendChannel<TServerToClientMessage> SendChannel { get; }
+	public Guid SessionId => session.SessionId;
+	public MessageSender<TServerToClientMessage> MessageSender => session.MessageSender;
 	
-	internal RpcServerToClientConnection(RpcServerClientSessions<TServerToClientMessage> sessions, Guid sessionId, MessageRegistry<TClientToServerMessage> messageRegistry, Stream stream, RpcServerClientSession<TServerToClientMessage> session) {
-		this.loggerName = session.LoggerName;
-		this.logger = PhantomLogger.Create<RpcServerToClientConnection<TClientToServerMessage, TServerToClientMessage>>(loggerName);
-		this.sessions = sessions;
+	internal RpcServerToClientConnection(RpcCommonConnectionParameters connectionParameters, MessageRegistry<TClientToServerMessage> messageRegistry, RpcServerClientSessions<TServerToClientMessage> sessions, RpcServerClientSession<TServerToClientMessage> session, Stream stream) {
+		this.logger = PhantomLogger.Create<RpcServerToClientConnection<TClientToServerMessage, TServerToClientMessage>>(session.LoggerName);
+		this.connectionParameters = connectionParameters;
 		this.messageRegistry = messageRegistry;
-		this.messageReceiveTracker = session.MessageReceiveTracker;
+		this.sessions = sessions;
+		this.session = session;
 		this.stream = stream;
-		
-		this.SessionId = sessionId;
-		this.SendChannel = session.SendChannel;
 	}
 	
-	internal async Task Listen(IMessageReceiver<TClientToServerMessage> receiver) {
-		var messageHandler = new RpcMessageHandler<TClientToServerMessage>(receiver, SendChannel);
-		var frameReader = new RpcFrameReader<TServerToClientMessage, TClientToServerMessage>(loggerName, messageRegistry, messageReceiveTracker, messageHandler, SendChannel);
+	internal async Task Listen(IMessageReceiver<TClientToServerMessage> messageReceiver) {
+		var messageHandler = new MessageHandler<TClientToServerMessage>(messageReceiver, session.FrameSender);
+		var frameReader = new RpcFrameReader<TServerToClientMessage, TClientToServerMessage>(session.LoggerName, connectionParameters, messageRegistry, messageHandler, MessageSender, session.FrameSender);
 		try {
 			await IFrame.ReadFrom(stream, frameReader, closeCancellationTokenSource.Token);
 		} catch (OperationCanceledException) {

Utils/Phantom.Utils/Collections/RangeSet.cs

@@ -38,7 +38,15 @@ public sealed class RangeSet<T> : IEnumerable<RangeSet<T>.Range> where T : IBina
 		return true;
 	}
 	
-	public IEnumerator<Range> GetEnumerator() {
+	public void Clear() {
+		ranges.Clear();
+	}
+	
+	public List<Range>.Enumerator GetEnumerator() {
+		return ranges.GetEnumerator();
+	}
+	
+	IEnumerator<Range> IEnumerable<Range>.GetEnumerator() {
 		return ranges.GetEnumerator();
 	}
 	

Web/Phantom.Web.Services/Rpc/ControllerConnection.cs

@@ -1,19 +1,19 @@
 using Phantom.Common.Messages.Web;
 using Phantom.Utils.Actor;
-using Phantom.Utils.Rpc.Runtime;
+using Phantom.Utils.Rpc.Message;
 
 namespace Phantom.Web.Services.Rpc;
 
-public sealed class ControllerConnection(RpcSendChannel<IMessageToController> connection) {
+public sealed class ControllerConnection(MessageSender<IMessageToController> sender) {
 	public ValueTask Send<TMessage>(TMessage message) where TMessage : IMessageToController {
-		return connection.SendMessage(message);
+		return sender.Send(message);
 	}
 	
 	public Task<TReply> Send<TMessage, TReply>(TMessage message, TimeSpan waitForReplyTime, CancellationToken waitForReplyCancellationToken = default) where TMessage : IMessageToController, ICanReply<TReply> {
-		return connection.SendMessage<TMessage, TReply>(message, waitForReplyTime, waitForReplyCancellationToken);
+		return sender.Send<TMessage, TReply>(message, waitForReplyTime, waitForReplyCancellationToken);
 	}
 	
 	public Task<TReply> Send<TMessage, TReply>(TMessage message, CancellationToken waitForReplyCancellationToken) where TMessage : IMessageToController, ICanReply<TReply> {
-		return connection.SendMessage<TMessage, TReply>(message, Timeout.InfiniteTimeSpan, waitForReplyCancellationToken);
+		return sender.Send<TMessage, TReply>(message, Timeout.InfiniteTimeSpan, waitForReplyCancellationToken);
 	}
 }

Web/Phantom.Web/Program.cs

@@ -6,6 +6,7 @@ using Phantom.Utils.Cryptography;
 using Phantom.Utils.IO;
 using Phantom.Utils.Logging;
 using Phantom.Utils.Rpc.Message;
+using Phantom.Utils.Rpc.Runtime;
 using Phantom.Utils.Rpc.Runtime.Client;
 using Phantom.Utils.Runtime;
 using Phantom.Utils.Threading;
@@ -59,8 +60,12 @@ try {
 		CertificateThumbprint: webKey.Value.CertificateThumbprint,
 		AuthToken: webKey.Value.AuthToken,
 		Handshake: new IRpcClientHandshake.NoOp(),
-		SendQueueCapacity: 500,
-		PingInterval: TimeSpan.FromSeconds(10)
+		CommonParameters: new RpcCommonConnectionParameters(
+			MessageQueueCapacity: 250,
+			FrameQueueCapacity: 500,
+			MaxConcurrentlyHandledMessages: 100,
+			PingInterval: TimeSpan.FromMinutes(1)
+		)
 	);
 	
 	using var rpcClient = await RpcClient<IMessageToController, IMessageToWeb>.Connect("Controller", rpcClientConnectionParameters, WebMessageRegistries.Definitions, shutdownCancellationToken);
@@ -70,7 +75,7 @@ try {
 	}
 	
 	var webConfiguration = new WebLauncher.Configuration(PhantomLogger.Create("Web"), webServerHost, webServerPort, webBasePath, dataProtectionKeysPath, shutdownCancellationToken);
-	var webApplication = WebLauncher.CreateApplication(webConfiguration, applicationProperties, rpcClient.SendChannel);
+	var webApplication = WebLauncher.CreateApplication(webConfiguration, applicationProperties, rpcClient.MessageSender);
 	
 	using var actorSystem = ActorSystemFactory.Create("Web");
 	
@@ -98,7 +103,7 @@ try {
 		PhantomLogger.Root.Information("Unregistering web...");
 		try {
 			using var unregisterCancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(10));
-			await rpcClient.SendChannel.SendMessage(new UnregisterWebMessage(), unregisterCancellationTokenSource.Token);
+			await rpcClient.MessageSender.Send(new UnregisterWebMessage(), unregisterCancellationTokenSource.Token);
 		} catch (OperationCanceledException) {
 			PhantomLogger.Root.Warning("Could not unregister web after shutdown.");
 		} catch (Exception e) {

Web/Phantom.Web/WebLauncher.cs

@@ -1,6 +1,6 @@
 using Microsoft.AspNetCore.DataProtection;
 using Phantom.Common.Messages.Web;
-using Phantom.Utils.Rpc.Runtime;
+using Phantom.Utils.Rpc.Message;
 using Phantom.Web.Services;
 using Serilog;
 using ILogger = Serilog.ILogger;
@@ -12,7 +12,7 @@ static class WebLauncher {
 		public string HttpUrl => "http://" + Host + ":" + Port;
 	}
 	
-	internal static WebApplication CreateApplication(Configuration config, ApplicationProperties applicationProperties, RpcSendChannel<IMessageToController> sendChannel) {
+	internal static WebApplication CreateApplication(Configuration config, ApplicationProperties applicationProperties, MessageSender<IMessageToController> sendChannel) {
 		var assembly = typeof(WebLauncher).Assembly;
 		var builder = WebApplication.CreateBuilder(new WebApplicationOptions {
 			ApplicationName = assembly.GetName().Name,