Unity TCP Server Hang Unity scene - unity3d

Question

I am trying to implement a TCP server in unity. I am using unity pro 3.5 and when I run this code in a scene, then unity hang, no response at all untill I kill it with Task Manager.
using UnityEngine;
using System.Collections;
using System.Net.Sockets;
using System.Net;
using System.Text;
public class Server : MonoBehaviour {
private IPAddress ipAd;
public string IP="127.0.0.1";
public int port = 8001;
private Socket s;
void Update ()
{
}
// Use this for initialization
void Awake () {
port = 8001;
ipAd = IPAddress.Parse(IP);
msg = "Listening at " + IP + ":" + port.ToString();
this.s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
this.s.Bind(new IPEndPoint(ipAd,port));
this.s.Listen(200);
while (true)
this.ReceiveMessage(this.s.Accept()); //hang if this line activated
}
private void ReceiveMessage(Socket socket)
{
byte[] tempbuffer = new byte[10000];
socket.Receive(tempbuffer);
rec.AssignFromByteArray(tempbuffer);
}
}

Answer 1

Server should run in it's own thread so the GameLoop can continue even if tcp_Listener.AcceptSocket() is a blocking call.
using UnityEngine;
using System.Collections;
using System.Threading;
using System.Net;
using System.Net.Sockets;
using System.IO;
public class Server : MonoBehaviour {
private bool mRunning;
public static string msg = "";
public Thread mThread;
public TcpListener tcp_Listener = null;
void Awake() {
mRunning = true;
ThreadStart ts = new ThreadStart(Receive);
mThread = new Thread(ts);
mThread.Start();
print("Thread done...");
}
public void stopListening() {
mRunning = false;
}
void Receive() {
tcp_Listener = new TcpListener(IPAddress.Parse("127.0.0.1"), 8001);
tcp_Listener.Start();
print("Server Start");
while (mRunning)
{
// check if new connections are pending, if not, be nice and sleep 100ms
if (!tcp_Listener.Pending()){
Thread.Sleep(100);
}
else {
Socket ss = tcp_Listener.AcceptSocket();
BonePos rec = new BonePos();
byte[] tempbuffer = new byte[10000];
ss.Receive(tempbuffer); // received byte array from client
rec.AssignFromByteArray(tempbuffer); // my own datatype
}
}
}
void Update() {
}
void OnApplicationQuit() { // stop listening thread
stopListening();// wait for listening thread to terminate (max. 500ms)
mThread.Join(500);
}
}
See Related answer from answers.unity3d.com

Answer 2

You get the hanging because of this:
while (true)
this.ReceiveMessage(this.s.Accept()); //hang if this line activated
The entire process is stuck in this loop, so nothing else gets processed.
What you could do (though I would not recommend it) is to perform the action inside update() instead of an infinite loop.
what I suggest is to use something else to run your server instead of unity.
If you are creating a game server, you can use PUN (Photon Unity Networking) or write a standalone server in C#, or even an open-sourced server in python that matches your needs.

Answer 3

You have to get rid of this statement:
while (true)
this.ReceiveMessage(this.s.Accept());
And your server has to run in his own thread.

Answer 4

Unity's engine is single threaded, and the life cycle methods of monobehaviours run synchronously in a predefined order. An infinite loop in one life cycle method will infinitely hang the program.
Coroutines are one way that you can create infinite loops without hanging indefinitely. This use case would likely make use of WaitForSeconds