No response from containers with port mapping

[sr258]

I'm trying to connect to a PostreSQL (standard one-click app) instance running with Caprover. I've tried exposing the container port 5432 on my host with port mappings, and weirdly, this works for some PostgreSQL clients, but not for others:

• I can connect and execute queries with Beekeeper Studio (Flatpak)
• I can connect and execute queries with Anatares SQL (Snap, uses pg NodeJS package internally)
• I cannot connect with psql or from my application code (using pq NodeJS package)

When trying to connect with psql, I simply get a blank line and nothing happens. I've also tried starting an ssh container (standard one-click app) in Caprover and do port forwarding with it. When I try to connect to this container with ssh, I see the same behavior as with psql: There's only a blank line and nothing happens. The verbose setting of ssh shows, that the server doesn't send any answer to the client. The last entry in the output is debug1: Local version string SSH-2.0-OpenSSH_8.9p1 Ubuntu-3ubuntu0.4. Next, you'd expect a response from the server giving its version, but there's nothing. I've tried this from various machines (MacBook, 2 x Ubuntu) and it's the same everywhere.

I'm clueless to what's going on. It's not a firewall issue, as the connection does work for some client applications. psql and ssh also establish a TCP connection, but then it looks like the servers refuse to answer.

Does anyone have an idea?

[sr258]

Man, the second I hit the submit button, it dawned on my that this might be an issue with using the hostname instead of the IP address. I I try to connect with the IPv4 address, things work regardless of the client! If I use the hostname, the clients that don't work use IPv6 and it doesn't work then. If I directly use the IP address, things are fine.