I'm working under WindowsCE/ PocketPC, but if anyone knows how to do this on a PC, then I would be interested in an answer. Basicly, I'm working on a utility that performs file transfers, and requires an internet connection. How do I check that there is a valid and active internet connection (if the user is already logged on), and if not, how do I call the "Establish Connection" dialog, so that the machine can dial the phone number, log on, etc...?

If the user is logged on you can send a ping packet to some site and wait for its ack

How to send a ping over inet(be careful its in german but with code)

Another tutorial but its using the UGLY!!!! windows api


concerning the other questions, under linux with dialups you can use ipppd ippp0 i think. As for broadband, you have to reinitialize your network connection, don t ask me for the command line option.
as for windows I dunno