description: Learn how to call gRPC services with the .NET gRPC client.
monikerRange: '>= aspnetcore-3.0'
ms.author: jamesnk
ms.date: 08/21/2019
uid: grpc/client
---
# Call gRPC services with the .NET client
A .NET gRPC client library is available in the [Grpc.Net.Client](https://www.nuget.org/packages/Grpc.Net.Client) NuGet package. This document explains how to:
* Configure a gRPC client to call gRPC services.
* Make gRPC calls to unary, server streaming, client streaming, and bi-directional streaming methods.
## Configure gRPC client
gRPC clients are concrete client types that are [generated from *\*.proto* files](xref:grpc/basics#generated-c-assets). The concrete gRPC client has methods that translate to the gRPC service in the *\*.proto* file.
A gRPC client is created from a channel. Start by using `GrpcChannel.ForAddress` to create a channel, and then use the channel to create a gRPC client:
```csharp
var channel = GrpcChannel.ForAddress("https://localhost:5001");
var client = new Greet.GreeterClient(channel);
```
A channel represents a long-lived connection to a gRPC service. When a channel is created it is configured with options related to calling a service. For example, the `HttpClient` used to make calls, the maximum send and receive message size, and logging can be specified on `GrpcChannelOptions` and used with `GrpcChannel.ForAddress`. For a complete list of options, see [client configuration options](xref:grpc/configuration#configure-client-options).
Creating a channel can be an expensive operation and reusing a channel for gRPC calls offers performance benefits. Multiple concrete gRPC clients can be created from a channel, including different types of clients. Concrete gRPC client types are lightweight objects and can be created when needed.
```csharp
var channel = GrpcChannel.ForAddress("https://localhost:5001");
var greeterClient = new Greet.GreeterClient(channel);
var counterClient = new Count.CounterClient(channel);
// Use clients to call gRPC services
```
`GrpcChannel.ForAddress` isn't the only option for creating a gRPC client. If you are calling gRPC services from an ASP.NET Core app, consider [gRPC client factory integration](xref:grpc/clientfactory). gRPC integration with `HttpClientFactory` offers a centralized alternative to creating gRPC clients.
> Additional configuration is required to [call insecure gRPC services with the .NET client](xref:grpc/troubleshoot#call-insecure-grpc-services-with-net-core-client).
A gRPC call is initiated by calling a method on the client. The gRPC client will handle message serialization and addressing the gRPC call to the correct service.
gRPC has different types of methods. How you use the client to make a gRPC call depends on the type of method you are calling. The gRPC method types are:
* Unary
* Server streaming
* Client streaming
* Bi-directional streaming
### Unary call
A unary call starts with the client sending a request message. A response message is returned when the service finishes.
```csharp
var client = new Greet.GreeterClient(channel);
var response = await client.SayHelloAsync(new HelloRequest { Name = "World" });
Each unary service method in the *\*.proto* file will result in two .NET methods on the concrete gRPC client type for calling the method: an asynchronous method and a blocking method. For example, on `GreeterClient` there are two ways of calling `SayHello`:
*`GreeterClient.SayHelloAsync` - calls `Greeter.SayHello` service asynchronously. Can be awaited.
*`GreeterClient.SayHello` - calls `Greeter.SayHello` service and blocks until complete. Don't use in asynchronous code.
### Server streaming call
A server streaming call starts with the client sending a request message. `ResponseStream.MoveNext()` reads messages streamed from the service. The server streaming call is complete when `ResponseStream.MoveNext()` returns `false`.
```csharp
var client = new Greet.GreeterClient(channel);
using (var call = client.SayHellos(new HelloRequest { Name = "World" }))
If you are using C# 8 or later then the `await foreach` syntax can be used to read messages. The `IAsyncStreamReader<T>.ReadAllAsync()` extension method reads all messages from the response stream:
```csharp
var client = new Greet.GreeterClient(channel);
using (var call = client.SayHellos(new HelloRequest { Name = "World" }))
{
await foreach (var response in call.ResponseStream.ReadAllAsync())
A client streaming call starts *without* the client sending a message. The client can choose to send sends messages with `RequestStream.WriteAsync`. When the client has finished sending messages `RequestStream.CompleteAsync` should be called to notify the service. The call is finished when the service returns a response message.
A bi-directional streaming call starts *without* the client sending a message. The client can choose to send messages with `RequestStream.WriteAsync`. Messages streamed from the service are accessible with `ResponseStream.MoveNext()` or `ResponseStream.ReadAllAsync()`. The bi-directional streaming call is complete when the `ResponseStream` has no more messages.
```csharp
using (var call = client.Echo())
{
Console.WriteLine("Starting background task to receive messages");
var readTask = Task.Run(async () =>
{
await foreach (var response in call.ResponseStream.ReadAllAsync())
{
Console.WriteLine(response.Message);
// Echo messages sent to the service
}
});
Console.WriteLine("Starting to send messages");
Console.WriteLine("Type a message to echo then press enter.");
while (true)
{
var result = Console.ReadLine();
if (string.IsNullOrEmpty(result))
{
break;
}
await call.RequestStream.WriteAsync(new EchoMessage { Message = result });
}
Console.WriteLine("Disconnecting");
await call.RequestStream.CompleteAsync();
await readTask;
}
```
During a bi-directional streaming call, the client and service can send messages to each other at any time. The best client logic for interacting with a bi-directional call varies depending upon the service logic.
