Nc won't send udp broadcast!?

Shell Programming and Scripting
1

Greetings,

I want to send broadcast udp from a script.

This works but is not broadcast:

echo -n "this is my message\r\n" | nc -u 192.168.0.12 5100

The broadcast version does not work:

echo -n "this is my message\r\n" | nc -u 192.168.0.255 5100

Suggestions on the right way to do this are welcome!

Thanks in advance,
Steve.

2

looking for the word 'broadcast' in the manual page for nc finds this:

       -b           allow UDP broadcasts
3

Interestingly enough, the -b option is only listed in the man page for some versions, but not others, of nc. I'm running both ubuntu and archlinux and have a different version on each (both are openBSD netcat though). I've tried -b on both and neither works. In the case where it's not listed in the man page, I get the expected "usage:..." response. In the one where it is listed in the man page I get "nc: Protocol not available". Both cases have been run from root...

I have not tried either the "traditional" netcat or the GNU netcat yet. I would be nice if someone out there actually knew if it worked and on what...

Or if someone could suggest a better way to do it...

---------- Post updated at 09:01 PM ---------- Previous update was at 04:42 PM ----------

never got nc to work and found many messages on the web regarding others who also couldn't get it to work. However, the following (from itsaunixsystem.com/unix/?p=5) does work as expected:

echo -n "message\r\n" | socat - udp-datagram:192.168.0.255:5100,broadcast