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Networking and servers • Re: Can only ping & SSH, despite no firewall (Bookworm)

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pi4@raspberrypi:~ $ nc -l 5000
That does not listen on port 5000. I think it means to listen (on next available port) for connections from host 5000 (which would be 0.0.19.136). The proper syntax is nc -l -p 5000.

There are at least three different implementations of netcat available in Debian, so it is possible your buster system was using a different one.

Code:

root@pi02:~# nc -l 5000GET / HTTP/1.1Host: pi02:5000User-Agent: curl/8.13.0Accept: */*root@pi02:~# netstat -anp | grep LIST | grep nctcp        0      0 0.0.0.0:5000            0.0.0.0:*               LISTEN      15916/nc            [clever@amd-nixos:~]$ curl pi02:5000root@pi02:~# which nc/usr/bin/ncroot@pi02:~# dpkg -L  netcat-openbsd/bin/nc.openbsdroot@pi02:~# ls -l /bin/nc /etc/alternatives/nclrwxrwxrwx 1 root root 20 Dec  5  2023 /bin/nc -> /etc/alternatives/nclrwxrwxrwx 1 root root 15 Dec  5  2023 /etc/alternatives/nc -> /bin/nc.openbsd
on my pi, which happens to be using the openbsd netcat, that syntax works just fine

Whoa, good catch, I was not aware of the subtle variations in syntax. However, it seems like this is not my issue. I took netcat out of the equation and switched to testing with a tiny web server.
what does "ip addr" return on the rpi

Statistics: Posted by cleverca22 — Sun May 25, 2025 10:39 pm



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