Program.cs

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Text;

// State object for receiving data from remote device.  
public class StateObject
{
    // Client socket.  
    public Socket workSocket = null;
    // Size of receive buffer.  
    public const int BufferSize = 256;
    // Receive buffer.  
    public byte[] buffer = new byte[BufferSize];
    // Received data string.  
    public StringBuilder sb = new StringBuilder();
}

public class AsynchronousClient
{
    // The port number for the remote device.  
    //private const int port = 11000;

    // ManualResetEvent instances signal completion.  
    private static ManualResetEvent connectDone =
        new ManualResetEvent(false);
    private static ManualResetEvent sendDone =
        new ManualResetEvent(false);
    private static ManualResetEvent receiveDone =
        new ManualResetEvent(false);

    // The response from the remote device.  
    private static String response = String.Empty;

    private static int Port;
    private static string Target;
    private static string Packet;
    private static bool Connected;
    private static bool EOF;
    private static void StartClient()
    {
        Console.ForegroundColor = ConsoleColor.White;
        Console.BackgroundColor = ConsoleColor.Blue;
        Console.Clear();
Console.WriteLine("  _   _      _   _    _             _    ");
Console.WriteLine(" | \\ | |    | | | |  | |           | |   ");
Console.WriteLine(" |  \\| | ___| |_| |__| | ___   ___ | | __");
Console.WriteLine(" | . ` |/ _ \\ __|  __  |/ _ \\ / _ \\| |/ /");
Console.WriteLine(" | |\\  |  __/ |_| |  | | (_) | (_) |   < ");
Console.WriteLine(" |_| \\_|\\___|\\__|_|  |_|\\___/ \\___/|_|\\_\\");
        Console.WriteLine();



        Connected = true;
        try
        {
            Console.Write("Input Port: "); Port = Convert.ToInt32(Console.ReadLine());
            Console.Write("Input IP: "); Target = Console.ReadLine();
            Console.Write("Send EOF: "); EOF = Convert.ToBoolean(Console.ReadLine().ToLower());
        }
        catch(Exception)
        {
            Connected = false;
        }

        // Connect to a remote device.  
        try
        {
            while (Connected == true)
            {
                // Establish the remote endpoint for the socket.  
                // The name of the   
                // remote device is "host.contoso.com".  
                IPHostEntry ipHostInfo = Dns.GetHostEntry(Target);
                IPAddress ipAddress = ipHostInfo.AddressList[0];
                IPEndPoint remoteEP = new IPEndPoint(ipAddress, Port);

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

                // Connect to the remote endpoint.  
                client.BeginConnect(remoteEP,
                    new AsyncCallback(ConnectCallback), client);
                connectDone.WaitOne();

                // Send test data to the remote device.  
                Console.Write("Send Packet: "); Packet = Console.ReadLine();
                Send(client, Packet + "<EOF>");
                sendDone.WaitOne();

                // Receive the response from the remote device.  
                Receive(client);
                receiveDone.WaitOne();

                // Write the response to the console.  
                Console.WriteLine("Response received : {0}", response);

                if(Connected == false)
                {
                    // Release the socket.  
                    client.Shutdown(SocketShutdown.Both);
                    client.Close();
                }

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

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

            // Complete the connection.  
            client.EndConnect(ar);

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

            // Signal that the connection has been made.  
            connectDone.Set();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void Receive(Socket client)
    {
        try
        {
            // Create the state object.  
            StateObject state = new StateObject();
            state.workSocket = client;

            // Begin receiving the data from the remote device.  
            client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReceiveCallback), state);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void ReceiveCallback(IAsyncResult ar)
    {
        try
        {
            // Retrieve the state object and the client socket   
            // from the asynchronous state object.  
            StateObject state = (StateObject)ar.AsyncState;
            Socket client = state.workSocket;

            // Read data from the remote device.  
            int bytesRead = client.EndReceive(ar);

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

                // Get the rest of the data.  
                client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReceiveCallback), state);
            }
            else
            {
                // All the data has arrived; put it in response.  
                if (state.sb.Length > 1)
                {
                    response = state.sb.ToString();
                }
                // Signal that all bytes have been received.  
                receiveDone.Set();
            }
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    private static void Send(Socket client, 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.  
        client.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), client);
    }

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

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

            // Signal that all bytes have been sent.  
            sendDone.Set();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

    public static int Main(String[] args)
    {
        StartClient();
        return 0;
    }
}