http://www.cs.odu.edu/~cs476/fall03/lectures/sockets.htm
http://www.cs.odu.edu/~cs476/fall03/lectures/sockets.htm
http://www.binarytides.com/programming-udp-sockets-c-linux/
http://www.binarytides.com/programming-udp-sockets-c-linux/
error codes
http://www.ioplex.com/~miallen/errcmp.html