final submitted version
added infrastructure for submitting from command line
passed public test 1, attempts to debug p2
close send socket, we dont' need it
bugfixes
doing everything in only one send/recv call
don't report success if the header is malformed.
implemented recv_msg
first attempt at recv
fixed init_{recv,send}_sd, minor refactoring, implemented pack_header, unpack_header, and send_msg. Tested with wireshark -- we're sending something.