3 ms·

Your observation doesn't contradict the use of firewall rules to accomplish this.

• rockskon 2y ago
  It's not some ufw rule that normally prevents hosting a service on port 0.
  • arghwhat 2y ago
    That's not what was said. They said that a firewall rule can redirect traffic coming in on port 0 to a running service even when a service cannot bind directly to port 0. Binding with port 0 as argument for AF_INET binds a random available port, not port 0. This is documented behavior of Linux and likely every other OS implementing a BSD-style socket interface. Also note that ufw is just a tiny, non-standard wrapper for the much more powerful nftables/iptables interfaces