cln-grpc not opening its port

[cvx35isl]

trying out cln-grpc with current v25.12, I put grpc-port=9777 into lightningd.conf and restarted.

It now says

...
2025-12-27T22:23:12.408Z INFO    plugin-cln-grpc: Connecting to "lightning-rpc" and serving grpc on 127.0.0.1:9777
2025-12-27T22:23:12.516Z INFO    lightningd: JSON COMMAND listconfigs: Invalid parameter config (Unknown config option): token '"hold-grpc-host"'
...

thats that. It starts normally from here on and says nothing more on grpc.

With netcat I get connection refused or reset (not sure) immediately. Unless there is a iptables problem I dont know about, i'd say its closed.

What is it trying to tell here?

I dont see a "hold-grpc-host" parameter anywhere in my config nor in the docs. Nor do I issue that JSON listconfigs. This is pretty early at startup, when all plugins load. Dont thing I can send commands at this point.

I do see the *.pem files existing as the doc says. However, they were not created now but a year ago or so. Maybe from when I used cln-rest.

[daywalker90]

I'm taking a wild guess and say you are running summars v6.1.0 ?

It's the only plugin i know that checks for the hold-grpc-host config option. The log line is not an error and should be fine tho!

What netcat options did you use? I usually do sudo netcat -tulpn | grep 9777 which should show something like:

tcp 0 0 127.0.0.1:9777 0.0.0.0:* LISTEN XXXXXX/cln-grpc

[cvx35isl]

bet won! its summars 6.1.0. Upgraded it along the way with lightningd. before I had summars 5.2.0 due to forgetting to bump that version in my build script...

as for netcat I use nc -v <pod> <port>, from a busybox based container (Alpine Linux). It usually says <pod> (<pod ip>:<port>) open for things i can connect to, like port 9735. For grpc-port 9777 it exists 1 without any message.

in the lightningd pod I cant run netcat as your image does not have it (which I consider the right thing).

Since there is no grpc-bind-addr parameter in the doc: is it possible I just cant run this setup? With two pods that is?
As it specifically says serving grpc on 127.0.0.1:9777? That 127.0.0.1 is not reachable via the <pod ip> my other pod talks to. The grpc listener would need to open 0.0.0.0:9777 to have that working.

[daywalker90]

You can set grpc-host to whatever ip you need it to for your setup.

[cvx35isl]

just figured: dont even need netcat, /proc/<pid>/net/tcp has all the knowledge. So my port is indeed open. But on loopback only, in contrast to 9735.

grpc-host=0.0.0.0 makes it work.

Failed to spot this in the doc, thanks!