// call from transport update
public void RawReceive()
{
try
{
if (socket != null)
{
while (socket.Poll(0, SelectMode.SelectRead))
{
int msgLength = socket.ReceiveFrom(rawReceiveBuffer, ref remoteEndpoint);
// IMPORTANT: detect if buffer was too small for the
// received msgLength. otherwise the excess
// data would be silently lost.
// (see ReceiveFrom documentation)
if (msgLength <= rawReceiveBuffer.Length)
{
//Log.Debug($"KCP: client raw recv {msgLength} bytes = {BitConverter.ToString(buffer, 0, msgLength)}");
RawInput(rawReceiveBuffer, msgLength);
}
else
{
KCPLog.Error($"KCP ClientConnection: message of size {msgLength} does not fit into buffer of size {rawReceiveBuffer.Length}. The excess was silently dropped. Disconnecting.");
Disconnect();
}
}
}
}
// this is fine, the socket might have been closed in the other end
catch (SocketException) {}
}
public void Connect(string address, ushort port, bool noDelay, uint interval, int fastResend = 0, bool congestionWindow = true, uint sendWindowSize = Kcp.WND_SND, uint receiveWindowSize = Kcp.WND_RCV)
{
if (connected)
{
KCPLog.Warning("KCP: client already connected!");
return;
}
connection = new KcpClientConnection();
// setup events
connection.OnAuthenticated = () =>
{
KCPLog.Info($"KCP: OnClientConnected");
connected = true;
OnConnected.Invoke();
};
connection.OnData = (message) =>
{
//Log.Debug($"KCP: OnClientData({BitConverter.ToString(message.Array, message.Offset, message.Count)})");
OnData.Invoke(message);
};
connection.OnDisconnected = () =>
{
KCPLog.Info($"KCP: OnClientDisconnected");
connected = false;
connection = null;
OnDisconnected.Invoke();
};
// connect
connection.Connect(address, port, noDelay, interval, fastResend, congestionWindow, sendWindowSize, receiveWindowSize);
}
void SendReliable(KcpHeader header, ArraySegment <byte> content)
{
// 1 byte header + content needs to fit into send buffer
if (1 + content.Count <= kcpSendBuffer.Length) // TODO
{
// copy header, content (if any) into send buffer
kcpSendBuffer[0] = (byte)header;
if (content.Count > 0)
{
Buffer.BlockCopy(content.Array, content.Offset, kcpSendBuffer, 1, content.Count);
}
// send to kcp for processing
int sent = kcp.Send(kcpSendBuffer, 0, 1 + content.Count);
if (sent < 0)
{
KCPLog.Warning($"Send failed with error={sent} for content with length={content.Count}");
}
}
// otherwise content is larger than MaxMessageSize. let user know!
else
{
KCPLog.Error($"Failed to send reliable message of size {content.Count} because it's larger than ReliableMaxMessageSize={ReliableMaxMessageSize}");
}
}
void HandleDeadLink()
{
// kcp has 'dead_link' detection. might as well use it.
if (kcp.state == -1)
{
KCPLog.Warning("KCP Connection dead_link detected. Disconnecting.");
Disconnect();
}
}
void HandleTimeout(uint time)
{
// note: we are also sending a ping regularly, so timeout should
// only ever happen if the connection is truly gone.
if (time >= lastReceiveTime + TIMEOUT)
{
KCPLog.Warning($"KCP: Connection timed out after not receiving any message for {TIMEOUT}ms. Disconnecting.");
Disconnect();
}
}
public void Send(ArraySegment <byte> segment, KcpChannel channel)
{
if (connected)
{
connection.SendData(segment, channel);
}
else
{
KCPLog.Warning("KCP: can't send because client not connected!");
}
}
void SendUnreliable(ArraySegment <byte> message)
{
// message size needs to be <= unreliable max size
if (message.Count <= UnreliableMaxMessageSize)
{
// copy channel header, data into raw send buffer, then send
rawSendBuffer[0] = (byte)KcpChannel.Unreliable;
Buffer.BlockCopy(message.Array, 0, rawSendBuffer, 1, message.Count);
RawSend(rawSendBuffer, message.Count + 1);
}
// otherwise content is larger than MaxMessageSize. let user know!
else
{
KCPLog.Error($"Failed to send unreliable message of size {message.Count} because it's larger than UnreliableMaxMessageSize={UnreliableMaxMessageSize}");
}
}
public void TickIncoming()
{
uint time = (uint)refTime.ElapsedMilliseconds;
try
{
switch (state)
{
case KcpState.Connected:
{
TickIncoming_Connected(time);
break;
}
case KcpState.Authenticated:
{
TickIncoming_Authenticated(time);
break;
}
case KcpState.Disconnected:
{
// do nothing while disconnected
break;
}
}
}
catch (SocketException exception)
{
// this is ok, the connection was closed
KCPLog.Info($"KCP Connection: Disconnecting because {exception}. This is fine.");
Disconnect();
}
catch (ObjectDisposedException exception)
{
// fine, socket was closed
KCPLog.Info($"KCP Connection: Disconnecting because {exception}. This is fine.");
Disconnect();
}
catch (Exception ex)
{
// unexpected
KCPLog.Error(ex.ToString());
Disconnect();
}
}
public void Connect(string host, ushort port, bool noDelay, uint interval = Kcp.INTERVAL, int fastResend = 0, bool congestionWindow = true, uint sendWindowSize = Kcp.WND_SND, uint receiveWindowSize = Kcp.WND_RCV)
{
KCPLog.Info($"KcpClient: connect to {host}:{port}");
IPAddress[] ipAddress = Dns.GetHostAddresses(host);
if (ipAddress.Length < 1)
{
throw new SocketException((int)SocketError.HostNotFound);
}
remoteEndpoint = new IPEndPoint(ipAddress[0], port);
socket = new Socket(remoteEndpoint.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
socket.Connect(remoteEndpoint);
SetupKcp(noDelay, interval, fastResend, congestionWindow, sendWindowSize, receiveWindowSize);
// client should send handshake to server as very first message
SendHandshake();
RawReceive();
}
public void Start(ushort port)
{
// only start once
if (socket != null)
{
KCPLog.Warning("KCP: server already started!");
}
// listen
#if UNITY_SWITCH
// Switch does not support ipv6
socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
socket.Bind(new IPEndPoint(IPAddress.Any, port));
#else
socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Dgram, ProtocolType.Udp);
socket.DualMode = true;
socket.Bind(new IPEndPoint(IPAddress.IPv6Any, port));
#endif
}
void TickIncoming_Connected(uint time)
{
// detect common events & ping
HandleTimeout(time);
HandleDeadLink();
HandlePing(time);
HandleChoked();
// any reliable kcp message received?
if (ReceiveNextReliable(out KcpHeader header, out ArraySegment <byte> message))
{
// message type FSM. no default so we never miss a case.
switch (header)
{
case KcpHeader.Handshake:
{
// we were waiting for a handshake.
// it proves that the other end speaks our protocol.
KCPLog.Info("KCP: received handshake");
state = KcpState.Authenticated;
OnAuthenticated?.Invoke();
break;
}
case KcpHeader.Ping:
{
// ping keeps kcp from timing out. do nothing.
break;
}
case KcpHeader.Data:
case KcpHeader.Disconnect:
{
// everything else is not allowed during handshake!
KCPLog.Warning($"KCP: received invalid header {header} while Connected. Disconnecting the connection.");
Disconnect();
break;
}
}
}
}
// reads the next reliable message type & content from kcp.
// -> to avoid buffering, unreliable messages call OnData directly.
bool ReceiveNextReliable(out KcpHeader header, out ArraySegment <byte> message)
{
header = KcpHeader.Handshake;
message = null;
int msgSize = kcp.PeekSize();
if (msgSize > 0)
{
// only allow receiving up to buffer sized messages.
// otherwise we would get BlockCopy ArgumentException anyway.
if (msgSize <= kcpMessageBuffer.Length)
{
// receive from kcp
int received = kcp.Receive(kcpMessageBuffer, msgSize);
if (received >= 0)
{
// extract header & content without header
header = (KcpHeader)kcpMessageBuffer[0];
message = new ArraySegment <byte>(kcpMessageBuffer, 1, msgSize - 1);
lastReceiveTime = (uint)refTime.ElapsedMilliseconds;
return(true);
}
else
{
// if receive failed, close everything
KCPLog.Warning($"Receive failed with error={received}. closing connection.");
Disconnect();
}
}
// we don't allow sending messages > Max, so this must be an
// attacker. let's disconnect to avoid allocation attacks etc.
else
{
KCPLog.Warning($"KCP: possible allocation attack for msgSize {msgSize} > buffer {kcpMessageBuffer.Length}. Disconnecting the connection.");
Disconnect();
}
}
header = KcpHeader.Disconnect;
return(false);
}
// disconnect this connection
public void Disconnect()
{
// only if not disconnected yet
if (state == KcpState.Disconnected)
{
return;
}
// send a disconnect message
if (socket.Connected)
{
try
{
SendDisconnect();
kcp.Flush();
}
catch (SocketException)
{
// this is ok, the connection was already closed
}
catch (ObjectDisposedException)
{
// this is normal when we stop the server
// the socket is stopped so we can't send anything anymore
// to the clients
// the clients will eventually timeout and realize they
// were disconnected
}
}
// set as Disconnected, call event
KCPLog.Info("KCP Connection: Disconnected.");
state = KcpState.Disconnected;
OnDisconnected?.Invoke();
}
public void SendData(ArraySegment <byte> data, KcpChannel channel)
{
// sending empty segments is not allowed.
// nobody should ever try to send empty data.
// it means that something went wrong, e.g. in Mirror/DOTSNET.
// let's make it obvious so it's easy to debug.
if (data.Count == 0)
{
KCPLog.Warning("KcpConnection: tried sending empty message. This should never happen. Disconnecting.");
Disconnect();
return;
}
switch (channel)
{
case KcpChannel.Reliable:
SendReliable(KcpHeader.Data, data);
break;
case KcpChannel.Unreliable:
SendUnreliable(data);
break;
}
}
void HandleChoked()
{
// disconnect connections that can't process the load.
// see QueueSizeDisconnect comments.
// => include all of kcp's buffers and the unreliable queue!
int total = kcp.rcv_queue.Count + kcp.snd_queue.Count +
kcp.rcv_buf.Count + kcp.snd_buf.Count;
if (total >= QueueDisconnectThreshold)
{
KCPLog.Warning($"KCP: disconnecting connection because it can't process data fast enough.\n" +
$"Queue total {total}>{QueueDisconnectThreshold}. rcv_queue={kcp.rcv_queue.Count} snd_queue={kcp.snd_queue.Count} rcv_buf={kcp.rcv_buf.Count} snd_buf={kcp.snd_buf.Count}\n" +
$"* Try to Enable NoDelay, decrease INTERVAL, disable Congestion Window (= enable NOCWND!), increase SEND/RECV WINDOW or compress data.\n" +
$"* Or perhaps the network is simply too slow on our end, or on the other end.\n");
// let's clear all pending sends before disconnting with 'Bye'.
// otherwise a single Flush in Disconnect() won't be enough to
// flush thousands of messages to finally deliver 'Bye'.
// this is just faster and more robust.
kcp.snd_queue.Clear();
Disconnect();
}
}
public void RawInput(byte[] buffer, int msgLength)
{
// parse channel
if (msgLength > 0)
{
byte channel = buffer[0];
switch (channel)
{
case (byte)KcpChannel.Reliable:
{
// input into kcp, but skip channel byte
int input = kcp.Input(buffer, 1, msgLength - 1);
if (input != 0)
{
KCPLog.Warning($"Input failed with error={input} for buffer with length={msgLength - 1}");
}
break;
}
case (byte)KcpChannel.Unreliable:
{
// ideally we would queue all unreliable messages and
// then process them in ReceiveNext() together with the
// reliable messages, but:
// -> queues/allocations/pools are slow and complex.
// -> DOTSNET 10k is actually slower if we use pooled
// unreliable messages for transform messages.
//
// DOTSNET 10k benchmark:
// reliable-only: 170 FPS
// unreliable queued: 130-150 FPS
// unreliable direct: 183 FPS(!)
//
// DOTSNET 50k benchmark:
// reliable-only: FAILS (queues keep growing)
// unreliable direct: 18-22 FPS(!)
//
// -> all unreliable messages are DATA messages anyway.
// -> let's skip the magic and call OnData directly if
// the current state allows it.
if (state == KcpState.Authenticated)
{
// only process messages while not paused for Mirror
// scene switching etc.
// -> if an unreliable message comes in while
// paused, simply drop it. it's unreliable!
if (!paused)
{
ArraySegment <byte> message = new ArraySegment <byte>(buffer, 1, msgLength - 1);
OnData?.Invoke(message);
}
// set last receive time to avoid timeout.
// -> we do this in ANY case even if not enabled.
// a message is a message.
// -> we set last receive time for both reliable and
// unreliable messages. both count.
// otherwise a connection might time out even
// though unreliable were received, but no
// reliable was received.
lastReceiveTime = (uint)refTime.ElapsedMilliseconds;
}
else
{
// should never
KCPLog.Warning($"KCP: received unreliable message in state {state}. Disconnecting the connection.");
Disconnect();
}
break;
}
default:
{
// not a valid channel. random data or attacks.
KCPLog.Info($"Disconnecting connection because of invalid channel header: {channel}");
Disconnect();
break;
}
}
}
}
public void TickIncoming()
{
while (socket != null && socket.Poll(0, SelectMode.SelectRead))
{
try
{
int msgLength = socket.ReceiveFrom(rawReceiveBuffer, 0, rawReceiveBuffer.Length, SocketFlags.None, ref newClientEP);
//Log.Info($"KCP: server raw recv {msgLength} bytes = {BitConverter.ToString(buffer, 0, msgLength)}");
// calculate connectionId from endpoint
int connectionId = newClientEP.GetHashCode();
// IMPORTANT: detect if buffer was too small for the received
// msgLength. otherwise the excess data would be
// silently lost.
// (see ReceiveFrom documentation)
if (msgLength <= rawReceiveBuffer.Length)
{
// is this a new connection?
if (!connections.TryGetValue(connectionId, out KcpServerConnection connection))
{
// create a new KcpConnection
connection = new KcpServerConnection(socket, newClientEP, NoDelay, Interval, FastResend, CongestionWindow, SendWindowSize, ReceiveWindowSize);
// DO NOT add to connections yet. only if the first message
// is actually the kcp handshake. otherwise it's either:
// * random data from the internet
// * or from a client connection that we just disconnected
// but that hasn't realized it yet, still sending data
// from last session that we should absolutely ignore.
//
//
// TODO this allocates a new KcpConnection for each new
// internet connection. not ideal, but C# UDP Receive
// already allocated anyway.
//
// expecting a MAGIC byte[] would work, but sending the raw
// UDP message without kcp's reliability will have low
// probability of being received.
//
// for now, this is fine.
// setup authenticated event that also adds to connections
connection.OnAuthenticated = () =>
{
// only send handshake to client AFTER we received his
// handshake in OnAuthenticated.
// we don't want to reply to random internet messages
// with handshakes each time.
connection.SendHandshake();
// add to connections dict after being authenticated.
connections.Add(connectionId, connection);
KCPLog.Info($"KCP: server added connection({connectionId}): {newClientEP}");
// setup Data + Disconnected events only AFTER the
// handshake. we don't want to fire OnServerDisconnected
// every time we receive invalid random data from the
// internet.
// setup data event
connection.OnData = (message) =>
{
// call mirror event
//Log.Info($"KCP: OnServerDataReceived({connectionId}, {BitConverter.ToString(message.Array, message.Offset, message.Count)})");
OnData.Invoke(connectionId, message);
};
// setup disconnected event
connection.OnDisconnected = () =>
{
// flag for removal
// (can't remove directly because connection is updated
// and event is called while iterating all connections)
connectionsToRemove.Add(connectionId);
// call mirror event
KCPLog.Info($"KCP: OnServerDisconnected({connectionId})");
OnDisconnected.Invoke(connectionId);
};
// finally, call mirror OnConnected event
KCPLog.Info($"KCP: OnServerConnected({connectionId})");
OnConnected.Invoke(connectionId);
};
// now input the message & process received ones
// connected event was set up.
// tick will process the first message and adds the
// connection if it was the handshake.
connection.RawInput(rawReceiveBuffer, msgLength);
connection.TickIncoming();
// again, do not add to connections.
// if the first message wasn't the kcp handshake then
// connection will simply be garbage collected.
}
// existing connection: simply input the message into kcp
else
{
connection.RawInput(rawReceiveBuffer, msgLength);
}
}
else
{
KCPLog.Error($"KCP Server: message of size {msgLength} does not fit into buffer of size {rawReceiveBuffer.Length}. The excess was silently dropped. Disconnecting connectionId={connectionId}.");
Disconnect(connectionId);
}
}
// this is fine, the socket might have been closed in the other end
catch (SocketException) {}
}
// process inputs for all server connections
// (even if we didn't receive anything. need to tick ping etc.)
foreach (KcpServerConnection connection in connections.Values)
{
connection.TickIncoming();
}
// remove disconnected connections
// (can't do it in connection.OnDisconnected because Tick is called
// while iterating connections)
foreach (int connectionId in connectionsToRemove)
{
connections.Remove(connectionId);
}
connectionsToRemove.Clear();
}
// server & client need to send handshake at different times, so we need
// to expose the function.
// * client should send it immediately.
// * server should send it as reply to client's handshake, not before
// (server should not reply to random internet messages with handshake)
// => handshake info needs to be delivered, so it goes over reliable.
public void SendHandshake()
{
KCPLog.Info("KcpConnection: sending Handshake to other end!");
SendReliable(KcpHeader.Handshake, default);
}
void TickIncoming_Authenticated(uint time)
{
// detect common events & ping
HandleTimeout(time);
HandleDeadLink();
HandlePing(time);
HandleChoked();
// process all received messages
//
// Mirror scene changing requires transports to immediately stop
// processing any more messages after a scene message was
// received. and since we are in a while loop here, we need this
// extra check.
//
// note while that this is mainly for Mirror, but might be
// useful in other applications too.
//
// note that we check it BEFORE ever calling ReceiveNext. otherwise
// we would silently eat the received message and never process it.
while (!paused &&
ReceiveNextReliable(out KcpHeader header, out ArraySegment <byte> message))
{
// message type FSM. no default so we never miss a case.
switch (header)
{
case KcpHeader.Handshake:
{
// should never receive another handshake after auth
KCPLog.Warning($"KCP: received invalid header {header} while Authenticated. Disconnecting the connection.");
Disconnect();
break;
}
case KcpHeader.Data:
{
// call OnData IF the message contained actual data
if (message.Count > 0)
{
//Log.Warning($"Kcp recv msg: {BitConverter.ToString(message.Array, message.Offset, message.Count)}");
OnData?.Invoke(message);
}
// empty data = attacker, or something went wrong
else
{
KCPLog.Warning("KCP: received empty Data message while Authenticated. Disconnecting the connection.");
Disconnect();
}
break;
}
case KcpHeader.Ping:
{
// ping keeps kcp from timing out. do nothing.
break;
}
case KcpHeader.Disconnect:
{
// disconnect might happen
KCPLog.Info("KCP: received disconnect message");
Disconnect();
break;
}
}
}
}