Why Can't My GRPC Client Connect to My Dockerized Server?

Cannot connect to a Go GRPC server running in a local Docker container

When running a GRPC client against a GRPC service running locally, it's important to consider the listening endpoint of the server. By default, when specifying a hostname or IP address (in this case, localhost), the server will only listen on that specific address.

In the context of Docker containers, listening on localhost (127.0.0.1) is problematic because it's not accessible outside the container. While Docker may expose ports on the host machine, the server will only listen on 127.0.0.1 within the container.

To resolve this issue, the listening endpoint should be changed to *:51672, instructing the server to listen on all available IP addresses within the container. This allows the container to receive traffic forwarded from the host machine on the exposed port.

To verify the problem, the iptables rules can be examined using the following commands:

iptables -n -L
iptables -t nat -n -L

These rules are created by Docker to implement port forwarding. By configuring the server to listen on all available IP addresses, the client can successfully connect to the GRPC service running within the Docker container.

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