client.cs

// gRPC channel
var channel = new Channel("127.0.0.1:50051", ChannelCredentials.Insecure);

// Protobuf service
var client = new Messenger.MessengerClient(channel);

// Protobuf model
var request = new HelloRequest { Name = "You" };

var reply = await client.SayHelloAsync(request);
channel.ShutdownAsync().Wait();

Messenger.proto

syntax = "proto3";

package AComms.Services;

// Client service definitions
service Messenger {
	// Send a greeting message
	rpc SayHello(HelloRequest) returns (HelloReply) {}
}

// The request message
message HelloRequest {
	string Name = 1;
}

message HelloReply {
	string message = 1;
}

Server.cs

namespace AComms
{
    internal class MessengerService : Messenger.MessengerBase
    {
        // Listen for SayHello requests from client and react.
        public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
        {
            return Task.FromResult(new HelloReply { Message = "Hello " + request.Name });
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var server = new Server
            {
                // Protobuf service
                Services = { Messenger.BindService(new MessengerService()) },
                Ports = { new ServerPort("localhost", 50051, ServerCredentials.Insecure) }
            };

            server.Start();
            Console.WriteLine("Server running\nPress any key to stop.");
            Console.ReadKey();

            server.ShutdownAsync().Wait();
        }
    }
}