You must have a server in someplace, either by IP or DNS lookup
You set the apn context, attach and you are connected
You may then send udp or tcp packets to your server
I also use rtp for VoIP + data
its kinda (press Start|Connect)
i c no trouble
I've implemented all from single uart port, no os, no winsock, no nothing
can be done by a pic and some 2k ram
About the Modem+SIM not having a fixed ip, this is nonsense. The modem
will connect when there is relevant info to send, or u may wake it up by calling or sending a sms
best
Pads