How do I fix 502 Bad Gateway with an Nginx reverse proxy on my home server?

[JosephJ]

I’ve been trying to set up a reverse proxy with Nginx on my home server, but I keep running into 502 Bad Gateway errors. I’ve double-checked that my backend service is running on the correct port and that my firewall rules are set, but the connection still seems to fail.

[Sofia35]

I had a similar 502 when the backend would not answer after a restart The nginx log pointed to a gateway timeout and the firewall was fine The real blocker was that the service did not listen on the expected port right after the restart

[Gregory.S]

Sometimes the problem is not the port but the backend listening on a unix socket and nginx trying to reach a network port I chased port numbers for hours before a note in the docs about sockets finally helped

[Jason37]

Another time I found the backend died after a noisy request The proxy would connect and then nginx reported bad gateway The fix was to add a longer timeout and watch the backend memory and crash log

[Penelope42]

Are we sure the 502 is the real issue here or could something upstream be failing before the proxy sees it