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

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

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

        private static readonly ManualResetEvent sendDone =
            new ManualResetEvent(false);

        private static readonly ManualResetEvent receiveDone =
            new ManualResetEvent(false);

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

        private static void StartClient()
        {
            // Connect to a remote device.
            try
            {
                // Establish the remote endpoint for the socket.
                // The name of the 
                // remote device is "host.contoso.com".
                var ipHostInfo = Dns.GetHostEntry("host.contoso.com");
                var ipAddress = ipHostInfo.AddressList[0];
                var remoteEP = new IPEndPoint(ipAddress, Port);

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

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

                // Send test data to the remote device.
                Send(client, "This is a test<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);

                // 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.
                var client = (Socket) ar.AsyncState;

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

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

                // 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.
                var state = new StateObject {WorkSocket = client};

                // Begin receiving the data from the remote device.
                client.BeginReceive(state.Buffer, 0, StateObject.BufferSize, 0,
                                    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.
                var state = (StateObject) ar.AsyncState;
                var client = state.WorkSocket;

                // Read data from the remote device.
                var 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,
                                        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.
            var byteData = Encoding.ASCII.GetBytes(data);

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

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

                // Complete sending the data to the remote device.
                var 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());
            }
        }
    }
}