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));

            // Check for end-of-file tag. If it is not there, read
            // more data.
            content = state.sb.ToString();
            if (content.IndexOf("<EOF>") > -1)
            {
                // All the data has been read from the
                // client. Display it on the console.
                //Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
                //    content.Length, content);

                string recievedData = content.Replace("<EOF>", "");

                Console.WriteLine("Read {0} bytes from socket.", recievedData.Length);

                MessageParser mp = new MessageParser(recievedData);

                mp.parsing();

                mp.DoJob();

                Console.WriteLine(mp.Result_);

                //string sendData = "calculation queue number : " + AsynchronousSocketListener.InstrumentQueue_.Count;

                // Echo the data back to the client.
                Send(handler, mp.Result_);
            }
            else
            {
                // Not all data received. Get more.
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                                     new AsyncCallback(ReadCallback), state);
            }
        }
    }