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grpcipc

gRPC ServerPort.PickUnused - how will client connect?

When establishing the server-side of grpc you can specify that it automatically chooses an unused port for you. However, if you use this feature then how will the clients know which port to connect to since it is dynamic?

In my particular case, I'll be using local ipc, though I suppose the question can pertain to remote ipc as well.

https://grpc.github.io/grpc/csharp/api/Grpc.Core.ServerPort.html

Solution

  • They must be told.

    PickUnused is a convenience to save the server (developer) determining an available port. It does not change nor simplify the client's port determination.

    Clients need to know a remote host address (if any) and a socket/port in order to connect to a server.

    Host addresses can be looked up (e.g. DNS) and the only solutions for the socket's discovery are:

    1. Static (not PickUnused)
    2. Well-known e.g. HTTP on 80 and HTTP/S on 443
    3. Service|Port lookup (server publishes its port to some service discovery1)
    4. Port scanning

    1 -- Perhaps another gRPC service using PickUnused 😃 Turtles, all the way down!