Sending data repeatedly in a opened socket connection

Hi,
Can anybody help me how to create a socket connection  which should remains always open. Also i need to send data through the same connection in particular time intervals. I followed the "Stream programming guide for cocoa" - http://developer.apple.com/documentation/Cocoa/Conceptual/Streams/Articles/NetworkStreams.html#//apple_ref/doc/uid/20002277 .Using this i created a socket connection and send the data successfully. But i am not able to send the data repeatedly in the same connection. Please help me in this.
Thanks,
Ramesh.P