---
title: Inter-process communication with gRPC
author: jamesnk
description: Learn how to use gRPC for inter-process communication.
monikerRange: '>= aspnetcore-5.0'
ms.author: jamesnk
ms.date: 09/16/2020
uid: grpc/interprocess
---
# Inter-process communication with gRPC

By [James Newton-King](https://twitter.com/jamesnk)

gRPC calls between a client and service are usually sent over TCP sockets. TCP was designed for communicating across a network. [Inter-process communication (IPC)](https://wikipedia.org/wiki/Inter-process_communication) is more efficient than TCP when the client and service are on the same machine. This document explains how to use gRPC with custom transports in IPC scenarios.

## Server configuration

Custom transports are supported by [Kestrel](xref:fundamentals/servers/kestrel). Kestrel is configured in `Program.cs`:

```csharp
public static readonly string SocketPath = Path.Combine(Path.GetTempPath(), "socket.tmp");

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
            webBuilder.ConfigureKestrel(options =>
            {
                if (File.Exists(SocketPath))
                {
                    File.Delete(SocketPath);
                }
                options.ListenUnixSocket(SocketPath, listenOptions =>
                {
                    listenOptions.Protocols = HttpProtocols.Http2;
                });
            });
        });
```

The preceding example:

* Configures Kestrel's endpoints in `ConfigureKestrel`.
* Calls <xref:Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerOptions.ListenUnixSocket*> to listen to a [Unix domain socket (UDS)](https://wikipedia.org/wiki/Unix_domain_socket) with the specified path.
* Creates a UDS endpoint that isn't configured to use HTTPS. For information about enabling HTTPS, see [Kestrel HTTPS endpoint configuration](xref:fundamentals/servers/kestrel/endpoints#listenoptionsusehttps).

Kestrel has built-in support for UDS endpoints. UDS are supported on Linux, macOS and [modern versions of Windows](https://devblogs.microsoft.com/commandline/af_unix-comes-to-windows/).

## Client configuration

`GrpcChannel` supports making gRPC calls over custom transports. When a channel is created, it can be configured with a `SocketsHttpHandler` that has a custom `ConnectCallback`. The callback allows the client to make connections over custom transports and then send HTTP requests over that transport.

Unix domain sockets connection factory example:

```csharp
public class UnixDomainSocketConnectionFactory
{
    private readonly EndPoint _endPoint;

    public UnixDomainSocketConnectionFactory(EndPoint endPoint)
    {
        _endPoint = endPoint;
    }

    public async ValueTask<Stream> ConnectAsync(SocketsHttpConnectionContext _,
        CancellationToken cancellationToken = default)
    {
        var socket = new Socket(AddressFamily.Unix, SocketType.Stream, ProtocolType.Unspecified);

        try
        {
            await socket.ConnectAsync(_endPoint, cancellationToken).ConfigureAwait(false);
            return new NetworkStream(socket, true);
        }
        catch
        {
            socket.Dispose();
            throw;
        }
    }
}
```

Using the custom connection factory to create a channel:

```csharp
public static readonly string SocketPath = Path.Combine(Path.GetTempPath(), "socket.tmp");

public static GrpcChannel CreateChannel()
{
    var udsEndPoint = new UnixDomainSocketEndPoint(SocketPath);
    var connectionFactory = new UnixDomainSocketConnectionFactory(udsEndPoint);
    var socketsHttpHandler = new SocketsHttpHandler
    {
        ConnectCallback = connectionFactory.ConnectAsync
    };

    return GrpcChannel.ForAddress("http://localhost", new GrpcChannelOptions
    {
        HttpHandler = socketsHttpHandler
    });
}
```

Channels created using the preceding code send gRPC calls over Unix domain sockets. Support for other IPC technologies can be implemented using the extensibility in Kestrel and `SocketsHttpHandler`.