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));

                    SFC sfc = new SFC();
                    sfc.msg("HI!");

                    //  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)
                    {
                        SFC sfc = new SFC();
                        sfc.msg(state.sb.ToString());
                    }
                    // Signal that all bytes have been received.
                    SFC.receiveDone.Set();

                }
            }
            catch (Exception e)
            {
                SFC sfc = new SFC();

                sfc.msg(e.ToString());
            }
        }