Send Data to Client from Server

Hello everybody:
I am trying to send data from the server to the client using TCP/Ip. However I am getting System ArgumentNullException error. Can anyone tell me where I am going wrong..

Pls guide..

txtSend.Text=Senddata;
Byte [] msg = System.Text.Encoding.ASCII.GetBytes(Senddata);

stream.Write(msg,0,msg.Length);
MessageBox.Show("Sent: {0}",Senddata);