These are the current features of Hexinject:

Hexadecimal and raw data injection on the net
Sniff data in hexadecimal or raw format from the net
Data can be piped and easily manipulated
Raw network access cmdline framework
Automatically set the correct checksum (IP, TCP, UDP, ICMP)
Automatically set the correct packet length (IP, TCP, UDP, ICMP)

Download
http://sourceforge.net/projects/hexinject/files/