Tutorial: Create a gRPC client and server in ASP.NET Core

By John Luo

This tutorial shows how to create a .NET Core gRPC client and an ASP.NET Core gRPC Server.

At the end, you'll have a gRPC client that communicates with the gRPC Greeter service.

View or download sample code (how to download).

In this tutorial, you:

  • Create a gRPC Server.
  • Create a gRPC client.
  • Test the gRPC client service with the gRPC Greeter service.

Prerequisites

Create a gRPC service

  • Start Visual Studio and select Create a new project. Alternatively, from the Visual Studio File menu, select New > Project.

  • In the Create a new project dialog, select gRPC Service and select Next:

    Create a new project dialog

  • Name the project GrpcGreeter. It's important to name the project GrpcGreeter so the namespaces will match when you copy and paste code.

  • Select Create.

  • In the Create a new gRPC service dialog:

    • The gRPC Service template is selected.
    • Select Create.

Run the service

  • Press Ctrl+F5 to run the gRPC service without the debugger.

    Visual Studio runs the service in a command prompt.

The logs show the service listening on https://localhost:5001.

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

Note

The gRPC template is configured to use Transport Layer Security (TLS). gRPC clients need to use HTTPS to call the server.

macOS doesn't support ASP.NET Core gRPC with TLS. Additional configuration is required to successfully run gRPC services on macOS. For more information, see Unable to start ASP.NET Core gRPC app on macOS.

Examine the project files

GrpcGreeter project files:

  • greet.proto – The Protos/greet.proto file defines the Greeter gRPC and is used to generate the gRPC server assets. For more information, see Introduction to gRPC.
  • Services folder: Contains the implementation of the Greeter service.
  • appSettings.json – Contains configuration data, such as protocol used by Kestrel. For more information, see Configuration in ASP.NET Core.
  • Program.cs – Contains the entry point for the gRPC service. For more information, see .NET Generic Host.
  • Startup.cs – Contains code that configures app behavior. For more information, see App startup.

Create the gRPC client in a .NET console app

  • Open a second instance of Visual Studio and select Create a new project.
  • In the Create a new project dialog, select Console App (.NET Core) and select Next.
  • In the Name text box, enter GrpcGreeterClient and select Create.

Add required packages

The gRPC client project requires the following packages:

  • Grpc.Net.Client, which contains the .NET Core client.
  • Google.Protobuf, which contains protobuf message APIs for C#.
  • Grpc.Tools, which contains C# tooling support for protobuf files. The tooling package isn't required at runtime, so the dependency is marked with PrivateAssets="All".

Install the packages using either the Package Manager Console (PMC) or Manage NuGet Packages.

PMC option to install packages

  • From Visual Studio, select Tools > NuGet Package Manager > Package Manager Console

  • From the Package Manager Console window, run cd GrpcGreeterClient to change directories to the folder containing the GrpcGreeterClient.csproj files.

  • Run the following commands:

    Install-Package Grpc.Net.Client
    Install-Package Google.Protobuf
    Install-Package Grpc.Tools
    

Manage NuGet Packages option to install packages

  • Right-click the project in Solution Explorer > Manage NuGet Packages
  • Select the Browse tab.
  • Enter Grpc.Net.Client in the search box.
  • Select the Grpc.Net.Client package from the Browse tab and select Install.
  • Repeat for Google.Protobuf and Grpc.Tools.

Add greet.proto

  • Create a Protos folder in the gRPC client project.

  • Copy the Protos\greet.proto file from the gRPC Greeter service to the gRPC client project.

  • Edit the GrpcGreeterClient.csproj project file:

    Right-click the project and select Edit Project File.


  • Add an item group with a <Protobuf> element that refers to the greet.proto file:

    <ItemGroup>
      <Protobuf Include="Protos\greet.proto" GrpcServices="Client" />
    </ItemGroup>
    

Create the Greeter client

Build the project to create the types in the GrpcGreeter namespace. The GrpcGreeter types are generated automatically by the build process.

Update the gRPC client Program.cs file with the following code:

using System;
using System.Net.Http;
using System.Threading.Tasks;
using GrpcGreeter;
using Grpc.Net.Client;

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

Program.cs contains the entry point and logic for the gRPC client.

The Greeter client is created by:

  • Instantiating a GrpcChannel containing the information for creating the connection to the gRPC service.
  • Using the GrpcChannel to construct the Greeter client:
static async Task Main(string[] args)
{
    // The port number(5001) must match the port of the gRPC server.
    var channel = GrpcChannel.ForAddress("https://localhost:5001");
    var client =  new Greeter.GreeterClient(channel);
    var reply = await client.SayHelloAsync(
                      new HelloRequest { Name = "GreeterClient" });
    Console.WriteLine("Greeting: " + reply.Message);
    Console.WriteLine("Press any key to exit...");
    Console.ReadKey();
}

The Greeter client calls the asynchronous SayHello method. The result of the SayHello call is displayed:

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

Test the gRPC client with the gRPC Greeter service

  • In the Greeter service, press Ctrl+F5 to start the server without the debugger.
  • In the GrpcGreeterClient project, press Ctrl+F5 to start the client without the debugger.

The client sends a greeting to the service with a message containing its name, GreeterClient. The service sends the message "Hello GreeterClient" as a response. The "Hello GreeterClient" response is displayed in the command prompt:

Greeting: Hello GreeterClient
Press any key to exit...

The gRPC service records the details of the successful call in the logs written to the command prompt:

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:\GH\aspnet\docs\4\Docs\aspnetcore\tutorials\grpc\grpc-start\sample\GrpcGreeter
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/2 POST https://localhost:5001/Greet.Greeter/SayHello application/grpc
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'gRPC - /Greet.Greeter/SayHello'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'gRPC - /Greet.Greeter/SayHello'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished in 78.32260000000001ms 200 application/grpc

Note

The code in this article requires the ASP.NET Core HTTPS development certificate to secure the gRPC service. If the client fails with the message The remote certificate is invalid according to the validation procedure., the development certificate is not trusted. For instructions to fix this issue, see Trust the ASP.NET Core HTTPS development certificate on Windows and macOS.

gRPC not supported on Azure App Service

Warning

ASP.NET Core gRPC is not currently supported on Azure App Service or IIS. The HTTP/2 implementation of Http.Sys does not support HTTP response trailing headers which gRPC relies on. For more information, see this GitHub issue.

Next steps