How to capture gRPC keep alives with tcpdump?

Hello!

I've tried all the possible combinations of filters in `tcpdump` for later inspection to try to capture gRPC keep alive probes, but I can never see them in Wireshark. So I don't know if the changes I'm making to my Go code are actually taking effect. Does anyone have an ideia on how to configure `tcpdump` to capture keep alive probes?

I'm trying to capture those probes in different services running on the same host, so I'm basically using gRPC as a local IPC mechanism.

Thank you so much!