Can't connect to TCP port on Android
<p>I have an Android app (really Xamarin app) and I'm using Socket to listen on port 8888 on the <strong>Android</strong> app.
So, I want to connect to this port from another computer by tcp (from PC TO Android).</p>

<p>And, I receive the following error:</p>

<pre><code>No connection could be made because the target machine actively refused it.
error 10061
</code></pre>

<p>My code (I got it from MS examples) works for two console apps. But if Android is server it doesn't work.</p>

<p>I try ping phone from pc, and it is OK.</p>

<p><strong>My question: maybe should open a port? Or something else? How can I do this?</strong></p>

<p>I will gladly to listen any ideas. Thanks.</p>

<p>My server code. C#, Xamarin.</p>

<pre><code>using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using Android.Runtime;
using Java.Lang;
using Byte = System.Byte;
using Exception = System.Exception;
using String = System.String;
using StringBuilder = System.Text.StringBuilder;

// State object for reading client data asynchronously
public class StateObject
{
    // Client  socket.
    public Socket workSocket = null;
    // Size of receive buffer.
    public const int BufferSize = 1024;
    // Receive buffer.
    public byte[] buffer = new byte[BufferSize];
    // Received data string.
    public StringBuilder sb = new StringBuilder();
}

public class AsynchronousSocketListener
{
    // Thread signal.
    public static ManualResetEvent allDone = new ManualResetEvent(false);

    public AsynchronousSocketListener()
    {
    }

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

        IPAddress ipAddress = new IPAddress(new byte[] { 127, 0, 0, 1 });
        IPEndPoint remoteEP = new IPEndPoint(ipAddress, 8888);
        // Create a TCP/IP socket.
        Socket listener = new Socket(AddressFamily.InterNetwork,
            SocketType.Stream, ProtocolType.Tcp);

        // Bind the socket to the local endpoint and listen for incoming connections.
        try
        {
            listener.Bind(remoteEP);
            listener.Listen(100);

            while (true)
            {
                // Set the event to nonsignaled state.
                allDone.Reset();

                // Start an asynchronous socket to listen for connections.
                Console.WriteLine("Waiting for a connection...");
                listener.BeginAccept(
                    new AsyncCallback(AcceptCallback),
                    listener);



                // Wait until a connection is made before continuing.
                allDone.WaitOne();
            }

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }

        Console.WriteLine("\nPress ENTER to continue...");
        Console.Read();

    }

    public static void AcceptCallback(IAsyncResult ar)
    {
        // Signal the main thread to continue.
        allDone.Set();

        // Get the socket that handles the client request.
        Socket listener = (Socket)ar.AsyncState;
        Socket handler = listener.EndAccept(ar);

        // Create the state object.
        StateObject state = new StateObject();
        state.workSocket = handler;
        handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(ReadCallback), state);
    }

    public static void ReadCallback(IAsyncResult ar)
    {
        String content = String.Empty;

        // Retrieve the state object and the handler socket
        // from the asynchronous state object.
        StateObject state = (StateObject)ar.AsyncState;
        Socket handler = state.workSocket;

        // Read data from the client socket. 
        int bytesRead = handler.EndReceive(ar);

        if (bytesRead &gt; 0)
        {
            // There  might be more data, so store the data received so far.
            state.sb.Append(Encoding.ASCII.GetString(
                state.buffer, 0, bytesRead));

            // Check for end-of-file tag. If it is not there, read 
            // more data.
            content = state.sb.ToString();
            if (content.IndexOf("&lt;EOF&gt;") &gt; -1)
            {
                // All the data has been read from the 
                // client. Display it on the console.
                Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
                    content.Length, content);
                // Echo the data back to the client.
                Send(handler, content);

            }
            else
            {
                // Not all data received. Get more.
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            }
        }
    }

    private static void Send(Socket handler, String data)
    {
        // Convert the string data to byte data using ASCII encoding.
        byte[] byteData = Encoding.ASCII.GetBytes(data);

        // Begin sending the data to the remote device.
        handler.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), handler);
    }

    private static void SendCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the socket from the state object.
            Socket handler = (Socket)ar.AsyncState;

            // Complete sending the data to the remote device.
            int bytesSent = handler.EndSend(ar);
            Console.WriteLine("Sent {0} bytes to client.", bytesSent);

            handler.Shutdown(SocketShutdown.Both);
            handler.Close();

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

}
</code></pre>

<p>My client code. Just simple C# console app:</p>

<pre><code>using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class SynchronousSocketClient
{

    public static void StartClient() {
        // Data buffer for incoming data.
        byte[] bytes = new byte[1024];

        Console.WriteLine("Start!");

        // Connect to a remote device.
        try {
            // Establish the remote endpoint for the socket.
            // This example uses port 11000 on the local computer.


           IPAddress ipAddress = new IPAddress(new byte[] { 10, 0, 1, 173 });
         //   IPAddress ipAddress = new IPAddress(new byte[] { 127, 0, 0, 1 });
            IPEndPoint remoteEP = new IPEndPoint(ipAddress, 8888);

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

            // Connect the socket to the remote endpoint. Catch any errors.
            try {
                sender.Connect(remoteEP);

                Console.WriteLine("Socket connected to {0}",
                    sender.RemoteEndPoint.ToString());

                // Encode the data string into a byte array.
                byte[] msg = Encoding.ASCII.GetBytes("This is a test&lt;EOF&gt;");

                // Send the data through the socket.
                int bytesSent = sender.Send(msg);

                // Receive the response from the remote device.
                int bytesRec = sender.Receive(bytes);
                Console.WriteLine("Echoed test = {0}",
                    Encoding.ASCII.GetString(bytes,0,bytesRec));

                // Release the socket.
                sender.Shutdown(SocketShutdown.Both);
                sender.Close();

            } catch (ArgumentNullException ane) {
                Console.WriteLine("ArgumentNullException : {0}",ane.ToString());
            } catch (SocketException se) {

                Console.WriteLine("SocketException : {0}",se.ErrorCode);
                Console.WriteLine("SocketException : {0}",se.SocketErrorCode);
                Console.WriteLine("SocketException : {0}",se.ToString());
            } catch (Exception e) {
                Console.WriteLine("Unexpected exception : {0}", e.ToString());
            }

        } catch (Exception e) {
            Console.WriteLine( e.ToString());
        }
    }

}
</code></pre>