Socket-programming-with-TCP.md

Sending and receiving a message over TCP

These methods provide simple string-based communication over a TCP socket connection:

• Sending a message
• Receiving a message

Sending a message

The remoteHost and remotePort parameter values must match the device that is listening for incoming connections and will be receiving the message.

using System;
using System.IO;
using System.Threading.Tasks;
using Windows.Networking;
using Windows.Networking.Sockets;

public static async Task SendStringTcpAsync(HostName remoteHost, 
    string remotePort, string message)
{
    using (var socket = new StreamSocket())
    {
        await socket.ConnectAsync(remoteHost, remotePort);
        using (var writer = new StreamWriter(
            socket.OutputStream.AsStreamForWrite()))
        {
            await writer.WriteLineAsync(message);
            await writer.FlushAsync();
        }
    }
}

Usage

try
{
    await SendStringTcpAsync(new HostName("192.168.0.5"), 
        "56789", "Hello, world!");
}
catch (Exception)
{
    // Handle relevant errors. 
}

Receiving a message

The specified callback is called every time a message is received.

The return value is a cleanup action that you should call when you are finished receiving messages.

using System;
using System.IO;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.Networking.Sockets;

public static async Task<Action> ReceiveStringTcpAsync(string port,
    Action<string, StreamSocketInformation> callback)
{
    var socket = new StreamSocketListener();
    TypedEventHandler<StreamSocketListener, 
        StreamSocketListenerConnectionReceivedEventArgs> handler = 
        async (sender, args) => 
        {
            using (var reader = new StreamReader(
                args.Socket.InputStream.AsStreamForRead()))
            {
                string message = await reader.ReadLineAsync();
                callback(message, args.Socket.Information);
            }
        };

    socket.ConnectionReceived += handler;
    await socket.BindServiceNameAsync(port);

    Action cleanup = () =>
    {
        socket.ConnectionReceived -= handler;
        socket.Dispose();
    };
    return cleanup;
}

Usage

You can bind to any port that is not already being used by the device. If the port is already in use, the ReceiveStringTcpAsync method will throw an exception.

Action cleanup = null;
try
{
    cleanup = await ReceiveStringTcpAsync("56789", (message, information) =>
    {
        System.Diagnostics.Debug.WriteLine(
            $"\"{message}\" was received from {information.RemoteAddress}.");
    });
}
catch (Exception)
{
    // Handle relevant errors.
}

// Clean up resources at the appropriate place in your code.  
if (cleanup != null) cleanup();

See also

StreamSocket class
StreamSocketListener class
Exceptions in Windows.Networking.Sockets

Lambda expressions (anonymous methods using the "=>" syntax)
Interpolated strings (strings with a $ prefix)

For code that handles more complex TCP socket communication scenarios, see the P2PHelper project in the QuizGame sample.