I’m developing a Unity App which requires a TCP server. I’m a C# Newbie and when I implemented the TCP Server I used the following code which is modified from something that I found online.
I start the TCP Server by calling this function:
public static bool StartServer(int port, ITcpServer serverComm){
serverSocket = new TcpListener(IPAddress.Any,port);
keepServerAlive = true;
RxBuffer = new byte[1024];
comm = serverComm; // Just an interface for notifying of data received.
try {
serverSocketThread = new Thread( new ThreadStart(OnClientDataReceived) );
serverSocketThread.IsBackground = true;
serverSocket.Start();
serverSocketThread.Start();
}
catch (Exception e){
VMLog.error("Failed to start TCP Server. Reason: " + e.Message); // Basically the same same thing as Debug.Log for this question.
return false;
}
connectionStatus = ConnectionStatus.CONNECTING;
return true;
}
And the OnClientDataReceived Function looks like this:
private static void OnClientDataReceived(){
try {
UnityEngine.Debug.Log("[TCP] Inside the try");
while (keepServerAlive){
UnityEngine.Debug.Log("[TCP] Inside the keep server alive");
using (client = serverSocket.AcceptTcpClient()) {
UnityEngine.Debug.Log("[TCP] Inside the accept TCP Clent");
// Get a stream object for reading
using (NetworkStream stream = client.GetStream()) {
int length;
//UnityEngine.Debug.Log("Connected and waiting for incomming bytes");
UnityEngine.Debug.Log("[TCP] Inside the Get Stream");
// Read incomming stream into byte arrary.
while ( ((length = stream.Read(RxBuffer, 0, RxBuffer.Length)) != 0) && keepServerAlive) {
connectionStatus = ConnectionStatus.CONNECTED; // If we are getting data, we are connected.
UnityEngine.Debug.Log("[TCP] Received " + length + " bytes");
comm.dataReceived(length);
}
UnityEngine.Debug.Log("[TCP] After the while in the stream read");
keepServerAlive = false;
}
}
}
VMLog.log("TCP Listening stopped naturally");
connectionStatus = ConnectionStatus.NOT_CONNECTED;
comm.rxThreadIsDone();
}
catch (Exception e){
VMLog.error("Listening thread died. Reason: " + e.Message);
connectionStatus = ConnectionStatus.NOT_CONNECTED;
comm.rxThreadIsDone();
}
}
The question is: how can I modify the code of onDataReceived to be able to manually kill it withouth having to call the Thread.Abort() method and I can’t figure out how. I don’t see where I can put a boolean that gets constantly checked and when it’s value is false the thread would naturally die.
5
You could use a CancellationTokenSource & passing its CancellationToken to the thread so you can signal it when to stop. You can manage what happens when the token is cancelled inside your onDataReceived, check for the IsCancellationRequested property of a passed token.
More reading on Cancellation tokens and examples
1
You should probably change AcceptTcpClient to AcceptSocketAsync. That way you can give it a cancellation token. I would also recommend changing your code to wrap everything server related into a class, that way you can use IAsyncDisposable to simply dispose the server when you are done.
It might look something like this:
public class MyTcpServer : IAsyncDisposable
{
private readonly TcpListener serverSocket;
private CancellationTokenSource cancel = new CancellationTokenSource();
private Task worker;
public MyTcpServer(int port)
{
serverSocket = new TcpListener(IPAddress.Any, port);
worker = Task.Run(Worker);
}
private void Worker()
{
while (true)
{
cancel.Token.ThrowIfCancellationRequested();
using (var client = serverSocket.AcceptSocketAsync(cancel.Token))
{
...
}
}
}
public async ValueTask DisposeAsync()
{
cancel.Cancel();
try
{
await worker;
}
catch(OperationCanceledException){} // ignore
}
}
you also need to decide if you want to terminate existing connections immediately, or let them continue naturally.
If you do not have any special reason to use raw TCP I would also recommend using some higher level protocol and library. There are plenty to chose from, and these tend to be much easier to use than writing your own network code, and doing raw TCP well tend to be difficult. Take a look at gRPC, AMQP or MQTT if you want somewhere to start.