See Smart Messaging FAQ for messages:
http://www.forum.nokia.com/main/1,35452,1_2_5_5,00.html
You can use AT commands or PC Connectivity SDK for sending the
messages through your phone or then you can get direct connection
to your SC via internet. If that SC is provided by Nokia then check
CIMD interface:
http://www.forum.nokia.com/main/1,35452,1_2_9,00.html
BR
M, Forum Nokia