Simple socket server in Unity

Question

I want to use a C# plugin in my Unity project. That plugin should act as a server which will get values from a client so that I'd be able to use those values for further processing. The issue is that the server has infinite loop. And infinite loops cause Unity to hang. How to handle this?

EDIT: I'm attaching a code snippet of server program. In my opinion, there are 2 points which may be causing problem. The infinite loops and the point where program is suspended as commented in code:

void networkCode()
{
    // Data buffer for incoming data.
    byte[] bytes = new Byte[1024];

    // Establish the local endpoint for the socket.
    // Dns.GetHostName returns the name of the 
    // host running the application.
    IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
    IPAddress ipAddress = ipHostInfo.AddressList[0];
    IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 1755);

    // Create a TCP/IP socket.
    listener = new Socket(ipAddress.AddressFamily,
        SocketType.Stream, ProtocolType.Tcp);

    // Bind the socket to the local endpoint and 
    // listen for incoming connections.
    try
    {
        listener.Bind(localEndPoint);
        listener.Listen(10);

        // Start listening for connections.
        while (true)
        {
            // Program is suspended while waiting for an incoming connection.
            Debug.Log("HELLO");     //It works
            handler = listener.Accept();
            Debug.Log("HELLO");     //It doesn't work
            data = null;

            // An incoming connection needs to be processed.
            while (true)
            {
                bytes = new byte[1024];
                int bytesRec = handler.Receive(bytes);
                data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
                if (data.IndexOf("<EOF>") > -1)
                {
                    break;
                }

                System.Threading.Thread.Sleep(1);
            }   

            System.Threading.Thread.Sleep(1);
        }
    }
    catch (Exception e)
    {
        Debug.Log(e.ToString());
    }
}

EDIT: After help from @Programmer, the C# plugin is complete. But Unity is not reading the correct values. I'm attaching the Unity side code:

using UnityEngine;
using System;

using SyncServerDLL;    //That's our library

public class receiver : MonoBehaviour {

    SynchronousSocketListener obj;   //That's object to call server methods

    // Use this for initialization
    void Start() {
        obj = new SynchronousSocketListener ();
        obj.startServer ();
    }

    // Update is called once per frame
    void Update() {
        Debug.Log (obj.data);
    }
}

I have tested SynchronousSocketListener class thoroughly in Visual Studio. It is giving good results there.

Answer 1

Use Thread to do your server Listen and read and write actions. You can declare socket and other networkstream objects as public then initialize them in a thread function.

Unity does not work well with while loops in Threads and may freeze sometimes, but you can fix that by adding System.Threading.Thread.Sleep(1); in your while loop where you are reading or waiting for data to arrive from socket.

Make sure to stop the Thread in OnDisable() function. Do NOT access Unity API from the new Thread function. Just do only the socket stuff there and return the data to a public variable.

System.Threading.Thread SocketThread;
volatile bool keepReading = false;

// Use this for initialization
void Start()
{
    Application.runInBackground = true;
    startServer();
}

void startServer()
{
    SocketThread = new System.Threading.Thread(networkCode);
    SocketThread.IsBackground = true;
    SocketThread.Start();
}



private string getIPAddress()
{
    IPHostEntry host;
    string localIP = "";
    host = Dns.GetHostEntry(Dns.GetHostName());
    foreach (IPAddress ip in host.AddressList)
    {
        if (ip.AddressFamily == AddressFamily.InterNetwork)
        {
            localIP = ip.ToString();
        }

    }
    return localIP;
}


Socket listener;
Socket handler;

void networkCode()
{
    string data;

    // Data buffer for incoming data.
    byte[] bytes = new Byte[1024];

    // host running the application.
    Debug.Log("Ip " + getIPAddress().ToString());
    IPAddress[] ipArray = Dns.GetHostAddresses(getIPAddress());
    IPEndPoint localEndPoint = new IPEndPoint(ipArray[0], 1755);

    // Create a TCP/IP socket.
    listener = new Socket(ipArray[0].AddressFamily,
        SocketType.Stream, ProtocolType.Tcp);

    // Bind the socket to the local endpoint and 
    // listen for incoming connections.

    try
    {
        listener.Bind(localEndPoint);
        listener.Listen(10);

        // Start listening for connections.
        while (true)
        {
            keepReading = true;

            // Program is suspended while waiting for an incoming connection.
            Debug.Log("Waiting for Connection");     //It works

            handler = listener.Accept();
            Debug.Log("Client Connected");     //It doesn't work
            data = null;

            // An incoming connection needs to be processed.
            while (keepReading)
            {
                bytes = new byte[1024];
                int bytesRec = handler.Receive(bytes);
                Debug.Log("Received from Server");

                if (bytesRec <= 0)
                {
                    keepReading = false;
                    handler.Disconnect(true);
                    break;
                }

                data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
                if (data.IndexOf("<EOF>") > -1)
                {
                    break;
                }

                System.Threading.Thread.Sleep(1);
            }

            System.Threading.Thread.Sleep(1);
        }
    }
    catch (Exception e)
    {
        Debug.Log(e.ToString());
    }
}

void stopServer()
{
    keepReading = false;

    //stop thread
    if (SocketThread != null)
    {
        SocketThread.Abort();
    }

    if (handler != null && handler.Connected)
    {
        handler.Disconnect(false);
        Debug.Log("Disconnected!");
    }
}

void OnDisable()
{
    stopServer();
}