Can't reach my Node.js application

Greetings!

I would bet that your application is listening on 127.0.0.1, as opposed to the public interface. If you run netstat -tulpn you should see the applications listening, and it might look something like this:

[root@gateway] ~ # netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      693/systemd-resolve
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1392/sshd
tcp6       0      0 :::22                   :::*                    LISTEN      1392/sshd
udp        0      0 127.0.0.53:53           0.0.0.0:*                           693/systemd-resolve
udp        0      0 10.128.0.5:68           0.0.0.0:*                           673/systemd-network
udp        0      0 127.0.0.1:323           0.0.0.0:*                           1756/chronyd
udp6       0      0 ::1:323                 :::*                                1756/chronyd

Notice on my system that systemd-resolve is listening on 127.0.0.1, so it is only reachable internally. Meanwhile, sshd is listening on 0.0.0.0 which means all interfaces, making it accessible both internally and externally.

Your application most likely defines this somewhere in it’s configuration, and can be adjusted. If you’re not sure where, maybe a grep through it’s code can help, something like:

grep -R "127.0.0.1" *

Or even:

grep -R "localhost" *

If it isn’t configured anywhere, it’s probably an assumed default and it is required that you specifically define the value to change it.

Jarland