Getting started with grpc-dotnet in VS Code

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply);
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The response message containing the greetings.
message HelloReply {
  string message = 1;
}

2.3 Startup.cs file

Startup.cs is where the aspnet core service configuration happens. AddGrpc method enables grpc support for this aspnet core service

public void ConfigureServices(IServiceCollection services)
{
services.AddGrpc();
}

app.UseEndpoints(endpoints =>
{
endpoints.MapGrpcService<GreeterService>();
endpoints.MapGet("/", async context =>
{
await context.Response.WriteAsync("Communication with gRPC endpoints must be made through a gRPC client. To learn how to create a client, visit: https://go.microsoft.com/fwlink/?linkid=2086909");
});
});

Communication with gRPC endpoints must be made through a gRPC client. To learn how to create a client, visit: https://go.microsoft.com/fwlink/?linkid=2086909

Step 4 : Creating a gRPC Client

gRPC client can be any dotnet or non-dotnet based application which supports http2 protocol. Invoking grpc services directly from browser based web apps is not possible (at the time of this writing) as the browsers don’t natively support http2 yet. There are other frameworks like grpc-web which could help in those cases where grpc services can be invoked from JS directly. For this post, we will be creating a dotnet core client

4.1 Let’s create a new console application using the command

C:\Blog\firstgRPCClient>dotnet new console
The template "Console Application" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on C:\Blog\firstgRPCClient\firstgRPCClient.csproj...
Restore completed in 126.13 ms for C:\Blog\firstgRPCClient\firstgRPCClient.csproj.

Restore succeeded.

4.2 Add necessary nuget packages for client app

Below are the nuget packages that are required by the console app to talk to grpc service

1. Grpc.Net.Client – contains .NET Core client
2. Google.Protobuf – to enable protobuf in the project
3. Grpc.Tools – used while for tooling, especially while building the application

Run the below commands

C:\Blog\firstgRPCClient>dotnet add firstgRPCClient.csproj package Grpc.Net.Client

C:\Blog\firstgRPCClient>dotnet add firstgRPCClient.csproj package Google.Protobuf

C:\Blog\firstgRPCClient>dotnet add firstgRPCClient.csproj package Grpc.Tools

4.3 Add proto files 

We can copy the protos folder from the service project and paste it to the client project with the same path as protos/greet.proto .

After this we need to include this under the firstgRPCClient.csproj as below

Note that, in this case we are making the GrpcServices as Client whereas the server project will add it as server This setting will enable the Grpc.Tools to generate server and client specific code appropriately

4.4 Implement the gRPC Client

Building the project would create the GrpcGreeter types from the proto file. Now update the Program.cs file with the below main method implementation

static async Task Main(string[] args)
{
    // The port number(5001) must match the port of the gRPC server.
    using var channel = GrpcChannel.ForAddress("https://localhost:5001");
    var client =  new Greeter.GreeterClient(channel);
    var reply = await client.SayHelloAsync(
    new HelloRequest { Name = "Swaminathan Vetri" });
    Console.WriteLine("Greeting: " + reply.Message);
    Console.WriteLine("Press any key to exit..."); Console.ReadKey();
}

GrpcChannel is the type that should be used to establish the communication between client and server listening at https://localhost:5001

Once the connection is established, we can create the client and then invoke the RPC methods by passing the required parameters

Step 5 : Testing the grpc service & client

Navigate to the grpc service folder in command prompt and run the command dotnet run That should produce the output as follows :

C:\Blog\firstgRPCService>dotnet run
info: Microsoft.Hosting.Lifetime[0]
Now listening on: https://localhost:5001
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: C:\Blog\firstgRPCService

Navigate to the grpc client folder in command prompt and run the command dotnet run

If the dotnet dev certs are not trusted yet in the machine, you might receive an error like this.

C:\Blog\firstgRPCClient>dotnet run
Unhandled exception. Grpc.Core.RpcException: Status(StatusCode=Internal, Detail="Error starting gRPC call: The SSL connection could not be established, see inner exception.")
at firstgRPCClient.Program.Main(String[] args) in C:\Blog\firstgRPCClient\Program.cs:line 15
at firstgRPCClient.Program.(String[] args)

To fix the above error, run the below command dotnet dev-certs https --trust

C:\Blog\firstgRPCClient>dotnet dev-certs https --trust
Trusting the HTTPS development certificate was requested. A confirmation prompt will be displayed if the certificate was not previously trusted. Click yes on the prompt to trust the certificate.
A valid HTTPS certificate is already present.

Now running the client project again, should succeed.

C:\Blog\firstgRPCClient>dotnet run
Greeting: Hello Swaminathan Vetri
Press any key to exit...

Well, we are done creating our first grpc unary service and a client! You can follow the same steps and add further proto files and defined more models & service methods.