Simple socket server in Unity

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();
}