Eh, nevermind again. I just re-read that place that said it was an erroneous error, and the guy was just speaking in a very unclear fashion. My original statement is re-instated. -.-
So is this actually a lower level thing than UDP? Since UDP doesnt do anything I wasnt expecting something like that.
Its really a lot useful..To handle "disconnection" this is a lot faster than waiting for a timeout.
Slightly lower-level. ICMP is part of the TCP/IP suite that handles control messages such as connection failure or pings. It's at the same level as a 'raw' socket (network layer), which UDP (transport layer) is a minimalist wrapper for.
The go-to book for this stuff is TCP/IP Illustrated, Vol. 1. You can get it used for about $10-20.