In testing certain network device driver receive features, I need to send special packets on the wire. I know I need to open a raw socket and push the bytes out. Is there some well-known example (C, perl, whatever) code already available for playing at this level?
(added later) I would prefer non-platform-specific answers, they'll be the most useful for everyone.
http://www.codeproject.com/KB/IP/sendrawpacket.aspx
There's already an existing project that may be able to help you with this.
I can't think of any examples. But you should just be able to open up a UDP socket to any IP address you like and start writing data to it. Make sure its UDP or this will not work.
Look at the documentation for packet. Basically, you create a socket with SOCK_RAW or SOCK_DGRAM, then write to the socket using normal socket i/o. However, the data you send will be put directly on the line, rather than automatically getting the headers that are necessary for most network interop.
I found that there's a good C example here at Security-Freak, which only needed a little modification for flexibility. I'm hoping there are more answers in other languages.
Check out http://tcpreplay.synfin.net/wiki/tcprewrite#RewritingLayer2 and http://tcpreplay.synfin.net/
Seems to me you are looking for a tool to generate your own packets, Scapy is such a tool often used in the security industry (such as pentesters).
Demo is available: http://www.secdev.org/projects/scapy/demo.html