Listen to UDP data on local port with netcat

Question

netcat -ul -p2115 fails with a usage statement.

What am I doing wrong?

score 95 · Accepted Answer · edited Jan 16 '19 at 11:49

To quote the nc man page:

-l Used to specify that nc should listen for an incoming connection rather than initiate a connection to a remote host. It is an error to use this option in conjunction with the -p, -s, or -z options. Additionally, any timeouts specified with the -w option are ignored.

The key here is that -p cannot be combined with the -l flag. When using the -l flag, any ports specified in the positional arguments are used. So instead, you could use the following:

netcat -ul 2115

score 30 · Answer 2 · edited Jan 18 '22 at 16:37

30

-p is wrong. This will work on RedHat- and Debian-based distros:

nc -u -l 2115

edited Jan 18 '22 at 16:37

Casey Jones

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answered Dec 01 '10 at 02:50

Mike

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score 12 · Answer 3 · answered Jul 16 '18 at 20:24

12

For some reason, Andrew's solution didn't work for me. With further research, I learned that we need to add -p flag when working locally. So the following command worked for me.

 nc -ulp 2115

answered Jul 16 '18 at 20:24

Sheshank Kodam

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Probably becuase there's two separate and subtly incompatible implementations of netcat in common use. – womble Jul 17 '18 at 00:21
I also had this problem on debian stretch. The version of netcat installed was `1.10-41`. – Ben Burns Apr 24 '20 at 21:38

Listen to UDP data on local port with netcat

3 Answers3