Hi Andy,
Thank you for the suggestion. Now my management changed idea and command me to do the thing in the other way. I mean my device will be a master and the program running on server must act as a passive slave.So i must send a determined sequence of commands and server executes and send me a response after each command.

They told me this the right way to do in a client-server system because the server can't handle complex sequences.

I give more details about the project, maybe this will help you to have a correct vision of the whole project.

My device will be connected at GPRS net and communicate with a server using UDP protocol. If the projects starts there will be potentially hundred thousands of devices located all around Europe.
This means the server must be able to handle thousands of concurrent connections, and is not possible to handle a conmplex sequence for each connection (maybe this will eat too much resources). Hope is more clear now.

As i said before i know very little about PC programming, so i have to think what they told me is right.What do you think about it?

Massimo.