How to create and use a TCP socket client application for Windows Phone [msdn]

1. Connect to the TCP socket server

Use the System. Net. Sockets API to create a socket and connect to the server. For clarity, the call to the System. Net. Sockets API is encapsulated in the SocketClient class.

Define the header (use _ socket variable storage)SocketObject. The _ clientDone variable is a ManualResetEvent used to coordinate asynchronous calls called through the Sockets API ):

 
// Cached Socket object that will be used by each call for the lifetime of this class
        Socket _socket = null;

        // Signaling object used to notify when an asynchronous operation is completed
        static ManualResetEvent _clientDone = new ManualResetEvent(false);

        // Define a timeout in milliseconds for each asynchronous call. If a response is not received within this 
        // timeout period, the call is aborted.
        const int TIMEOUT_MILLISECONDS = 5000;

        // The maximum size of the data buffer to use with the asynchronous socket methods
        const int MAX_BUFFER_SIZE = 2048;

In SocketClient. cs, add the following method to create a TCP socket and send an asynchronous connection request to the server. The response to this operation will be processed by the inline callback.

  public string Connect(string hostName, int portNumber)
        {
            string result = string.Empty;

            DnsEndPoint hostEntry = new DnsEndPoint(hostName, portNumber);

            _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            
            // Create a SocketAsyncEventArgs object to be used in the connection request
            SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
            socketEventArg.RemoteEndPoint = hostEntry;

            socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
            {
                result = e.SocketError.ToString();

                _clientDone.Set();
            });

            _clientDone.Reset();

            _socket.ConnectAsync(socketEventArg);

            _clientDone.WaitOne(TIMEOUT_MILLISECONDS);

            return result;
        }

2. send data to the TCP socket server

public string Send(string data)
        {
            string response = "Operation Timeout";

            // We are re-using the _socket object that was initialized in the Connect method
            if (_socket != null)
            {
                // Create SocketAsyncEventArgs context object
                SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();

                // Set properties on context object
                socketEventArg.RemoteEndPoint = _socket.RemoteEndPoint;
                socketEventArg.UserToken = null;

                // Inline event handler for the Completed event.
                // Note: This event handler was implemented inline in order to make this method self-contained.
                socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
                {
                    response = e.SocketError.ToString();

                    // Unblock the UI thread
                    _clientDone.Set();
                });

                // Add the data to be sent into the buffer
                byte[] payload = Encoding.UTF8.GetBytes(data);
                socketEventArg.SetBuffer(payload, 0, payload.Length);

                // Sets the state of the event to nonsignaled, causing threads to block
                _clientDone.Reset();

                // Make an asynchronous Send request over the socket
                _socket.SendAsync(socketEventArg);

                // Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.
                // If no response comes back within this time then proceed
                _clientDone.WaitOne(TIMEOUT_MILLISECONDS);
            }
            else
            {
                response = "Socket is not initialized";
            }

            return response;
        }

3. receive data from the TCP socket server

   public string Receive()
        {
            string response = "Operation Timeout";

            // We are receiving over an established socket connection
            if (_socket != null)
            {
                // Create SocketAsyncEventArgs context object
                SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
                socketEventArg.RemoteEndPoint = _socket.RemoteEndPoint;

                // Setup the buffer to receive the data
                socketEventArg.SetBuffer(new Byte[MAX_BUFFER_SIZE], 0, MAX_BUFFER_SIZE);

                // Inline event handler for the Completed event.
                // Note: This even handler was implemented inline in order to make this method self-contained.
                socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
                {
                    if (e.SocketError == SocketError.Success)
                    {
                        // Retrieve the data from the buffer
                        response = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);
                        response = response.Trim('\0');
                    }
                    else
                    {
                        response = e.SocketError.ToString();
                    }

                    _clientDone.Set();
                });

                // Sets the state of the event to nonsignaled, causing threads to block
                _clientDone.Reset();

                // Make an asynchronous Receive request over the socket
                _socket.ReceiveAsync(socketEventArg);

                // Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.
                // If no response comes back within this time then proceed
                _clientDone.WaitOne(TIMEOUT_MILLISECONDS);
            }
            else
            {
                response = "Socket is not initialized";
            }

            return response;
        }

        /// <summary>
        /// Closes the Socket connection and releases all associated resources
        /// </summary>
        public void Close()
        {
            if (_socket != null)
            {
                _socket.Close();
            }
        }