Re:Um what? (Score 1)

That doesn't happen. The big difference between most client server applications and SMS is that in SMS the server is actually capable of contacting the client. Your SMS client does not go onto the network to see if you have messages, but the SMSC (short message service center) will try to deliver your SMSes to you, and if you are not online, will try later or get paged when you get online so you receive your SMSes then. I'm not sure how that works with IM protocols.