by the sounds of things you want what sub 7 does.. a lame lil tool to give you the new ip address of sum1 when they connect.. the best way to do this is A)
write a tool that use the w32api refrence to check for an internet connection.. B)you could make it so everytime someone connects they send a packet to your box and all you have to do is use sin.addr to get their name c/c++/asm styles
if your on dialup and worried about ur ip changing and the method not being effective anymore use
and voila you have a webaddress that changes where it points 2
check out my site for a server to recieve the ip etc
non-blocking bind is what ur looking for
The wise make mistakes, the fools repeat them
When you have eliminated the impossible, that which remains, however improbable, must be the truth