A request to send or receive data was disallowed the socket is not connected

Question

I am trying ti print a string to an RFID Printer using sockets. Here is my code. When i call :

Print p = new Print();
p.printToIP();

I get this error: A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied.

Here is my class code:

class Print
{

    public string printerIP { get; set; }
    public int printerPort { get; set; }
    public string myZPL { get; set; }
    private EndPoint ep { get; set; }
    private Socket sock { get; set; }
    private NetworkStream ns { get; set; }
    //private AsyncCallback callbackWrite;

public Print()
{
    printerIP = "127.0.0.1";
    printerPort = 9001;
    myZPL = "AN12345";
}



public void printToIP()
{
    ep = new IPEndPoint(IPAddress.Parse(printerIP), printerPort);
    sock = new Socket(ep.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
    sock.Bind(ep);
    sock.Listen(10);

    try
    {
        sock.Connect(ep);
        ns = new NetworkStream(sock);
        byte[] toSend = Encoding.ASCII.GetBytes(myZPL);
        ns.BeginWrite(toSend, 0, toSend.Length, OnWriteComplete, null);
        ns.Flush(); 
    }
    catch (Exception ex)
    {
        sock.Shutdown(SocketShutdown.Both);
        sock.Close();
    }

}

private void OnWriteComplete(IAsyncResult ar)
{
    NetworkStream thisNS = ns;
    thisNS.EndWrite(ar);
    sock.Shutdown(SocketShutdown.Both);
    sock.Close();
}

Answer 1

You get this error because you sent data before your client connected .

 ....
     var res = sock .BeginAccept(AcceptCallback, null);

    }

    private void AcceptCallback(IAsyncResult result)
    {           
        Socket socket = sock .EndAccept(result);           

        while (true)
        {
            sock.BeginReceive(_buffer, 0, _buffer.Length, SocketFlags.None, 
                              new AsyncCallback(ReceiveCallBack), socket);
            _resetEvent.WaitOne();
            _resetEvent.Reset();
        }
    }


    ....

Answer 2

You should not use a listner socket to Transfer data, you should use a client socket for send or receive data, Usully listener sockets are used only a receiption. Use a client socket then your problem will be solved.

Here you are creating a Listner socket not a client socket

  sock = new Socket(ep.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
  sock.Bind(ep);
  sock.Listen(10);

The proper way would be to create a new instance of socket and connect it to Endpoints

And IF I were you i wouldn't use Socket class, instead I would use TCPClinet/ TCPListner classes provided by framwork.

For Tcpclinet class that would be like this

System.Net.Sockets.TcpClient clinet = new System.Net.Sockets.TcpClient();
            clinet.Connect(endpoint_object); 

For normal Socket class that would be this , So you must use the below code in your case

 Socket clientSock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
    clientSock.Connect(ipEnd);