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Accepted
Mike B
Asked: 2013-06-01 08:25:36 +0800 CST

How can I configure netcat (or some other stock linux utility) to listen on a specific port on a secondary IP address?

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CentOS 5.9

For testing purposes, I want my CentOS server to listen on a secondary virtual IP (eth0:0). I'm familiar with nc -l -p <port> but it only listens on the primary. Is there a way I can specify a specific IP for the listener to use?

If not, is there another "stock" utility in CentOS 5.9 that can do this?

linux

2 Answers

  1. Best Answer

    The syntax depends on the netcat package.

    netcat-openbsd

    nc -l 192.168.2.1 3000

    netcat-traditional

    nc -l -p 3000 -s 192.168.2.1

    A simple way (at least in bash) for telling them apart in scripts is:

    if ldd $(type -P nc) | grep -q libbsd; then
    nc -l 192.168.2.1 3000
else
    nc -l -p 3000 -s 192.168.2.1
fi
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  2. For completion:

    nc -l -p port -s ip

    should work too. Works with nc6 version 1.0 and netcat (The GNU Netcat) 0.7.1.

    The command from Laging doesn't work with nc6 (used in debian).

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