Netcat: using nc -l port_number instead of nc -l -p port_number

Question

This question is following this one: Sockets working in openSUSE do not work in Debian? When working with sockets on my Debian system, I have to use nc -l -p port_number to simulate the server I want to talk with. If I'm using nc -l port_number, it will fail when using the socket connect function and strerror(errno) will say "Connection refused". Netcat without -p option is working great on other Linux distributions, what should I change on my configuration?

Accepted Answer

I agree with duskwuff that it is better to just use the `-p` option everywhere, but to answer your question:

The one thing you have to do is install a netcat that supports the syntax you want. I know the `netcat-openbsd` package supports it. I know the `netcat-traditional` package does not. There's also a `netcat6` package, which also doesn't. You can then explicitly request the OpenBSD version of netcat like so:

```
nc.openbsd -l 4242
```

Optionally you may use the alternatives system to set this version of netcat to run when you issue the `nc` command:

```
update-alternatives --set nc /bin/nc.openbsd
```

This will be done automatically for you if this is the only netcat you've installed.

Finally, you may, again optionally, remove the netcat you don't like (`netcat-traditional` or `netcat6`).

Netcat: using nc -l port_number instead of nc -l -p port_number

Solution

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