我不能保持客户端与服务器的连接，也不能在客户端发出第一个请求后发送任何东西

我不能保持客户端连接到服务器或发送任何在客户端发出的第一个请求之后。我知道这是因为我在'SendCallback'方法关闭和关闭我的套接字，但否则它会向客户端发送垃圾邮件，直到客户端拒绝连接。我能做些什么来解决这个问题?希望我的解释足够清楚。

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 static ArrayList terminal = new ArrayList();
private List<StateObject> clients;
public AsynchronousSocketListener()
{
}
public static void StartListening()
{
    // Data buffer for incoming data.
    byte[] bytes = new Byte[1024];
    // Establish the local endpoint for the socket.
    IPHostEntry ipHostInfo = Dns.Resolve("192.168.1.75");
    IPAddress ipAddress = ipHostInfo.AddressList[0];
    IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 10008);
    // 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(localEndPoint);
        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();
            Console.WriteLine("Terminal Connected");
        }
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
    Console.WriteLine("Press 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 > 0)
    {
        // There  might be more data, so store the data received so far.
        state.sb.Append(Encoding.ASCII.GetString(
            state.buffer, 0, bytesRead));
        content = state.sb.ToString();
        Console.WriteLine( content );
        Send(handler);
     }
     else
     {
         Console.WriteLine("Failed to collect data.");
            // Not all data received. Get more.
            // Code would loop, leaving the server without answer.
            /*handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(ReadCallback), state);*/
     }
}
private static void Send(Socket handler)
{
    String data = String.Empty;
    Console.WriteLine("Sent Back:");
    data = ("002BSLL01V01000     DF02V0110");
    Console.WriteLine(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);
        Send(handler);
        handler.Shutdown(SocketShutdown.Both);
        handler.Close();
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}

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