---
title: Host ASP.NET Core SignalR in background services
author: bradygaster
description: Learn how to send messages to SignalR clients from .NET Core BackgroundService classes.
monikerRange: '>= aspnetcore-2.2'
ms.author: bradyg
ms.custom: mvc
ms.date: 11/12/2019
no-loc: [Home, Privacy, Kestrel, appsettings.json, "ASP.NET Core Identity", cookie, Cookie, Blazor, "Blazor Server", "Blazor WebAssembly", "Identity", "Let's Encrypt", Razor, SignalR]
uid: signalr/background-services
---
# Host ASP.NET Core SignalR in background services

By [Brady Gaster](https://twitter.com/bradygaster)

This article provides guidance for:

* Hosting SignalR Hubs using a background worker process hosted with ASP.NET Core.
* Sending messages to connected clients from within a .NET Core [BackgroundService](xref:Microsoft.Extensions.Hosting.BackgroundService).

::: moniker range=">= aspnetcore-3.0"

[View or download sample code](https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/signalr/background-service/samples/3.x) [(how to download)](xref:index#how-to-download-a-sample)

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

[View or download sample code](https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/signalr/background-service/samples/2.2) [(how to download)](xref:index#how-to-download-a-sample)

::: moniker-end

## Enable SignalR in startup

::: moniker range=">= aspnetcore-3.0"

Hosting ASP.NET Core SignalR Hubs in the context of a background worker process is identical to hosting a Hub in an ASP.NET Core web app. In the `Startup.ConfigureServices` method, calling `services.AddSignalR` adds the required services to the ASP.NET Core Dependency Injection (DI) layer to support SignalR. In `Startup.Configure`, the `MapHub` method is called in the `UseEndpoints` callback to connect the Hub endpoints in the ASP.NET Core request pipeline.

[!code-csharp[Startup](background-service/samples/3.x/Server/Startup.cs?name=Startup)]

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

Hosting ASP.NET Core SignalR Hubs in the context of a background worker process is identical to hosting a Hub in an ASP.NET Core web app. In the `Startup.ConfigureServices` method, calling `services.AddSignalR` adds the required services to the ASP.NET Core Dependency Injection (DI) layer to support SignalR. In `Startup.Configure`, the `UseSignalR` method is called to connect the Hub endpoint(s) in the ASP.NET Core request pipeline.

[!code-csharp[Startup](background-service/samples/2.2/Server/Startup.cs?name=Startup)]

::: moniker-end

In the preceding example, the `ClockHub` class implements the `Hub<T>` class to create a strongly typed Hub. The `ClockHub` has been configured in the `Startup` class to respond to requests at the endpoint `/hubs/clock`.

For more information on strongly typed Hubs, see [Use hubs in SignalR for ASP.NET Core](xref:signalr/hubs#strongly-typed-hubs).

> [!NOTE]
> This functionality isn't limited to the [Hub\<T>](xref:Microsoft.AspNetCore.SignalR.Hub`1) class. Any class that inherits from [Hub](xref:Microsoft.AspNetCore.SignalR.Hub), such as [DynamicHub](xref:Microsoft.AspNetCore.SignalR.DynamicHub), works.

::: moniker range=">= aspnetcore-3.0"

[!code-csharp[Startup](background-service/samples/3.x/Server/ClockHub.cs?name=ClockHub)]

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

[!code-csharp[Startup](background-service/samples/2.2/Server/ClockHub.cs?name=ClockHub)]

::: moniker-end

The interface used by the strongly typed `ClockHub` is the `IClock` interface.

::: moniker range=">= aspnetcore-3.0"

[!code-csharp[Startup](background-service/samples/3.x/HubServiceInterfaces/IClock.cs?name=IClock)]

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

[!code-csharp[Startup](background-service/samples/2.2/HubServiceInterfaces/IClock.cs?name=IClock)]

::: moniker-end

## Call a SignalR Hub from a background service

During startup, the `Worker` class, a `BackgroundService`, is enabled using `AddHostedService`.

```csharp
services.AddHostedService<Worker>();
```

Since SignalR is also enabled up during the `Startup` phase, in which each Hub is attached to an individual endpoint in ASP.NET Core's HTTP request pipeline, each Hub is represented by an `IHubContext<T>` on the server. Using ASP.NET Core's DI features, other classes instantiated by the hosting layer, like `BackgroundService` classes, MVC Controller classes, or Razor page models, can get references to server-side Hubs by accepting instances of `IHubContext<ClockHub, IClock>` during construction.

::: moniker range=">= aspnetcore-3.0"

[!code-csharp[Startup](background-service/samples/3.x/Server/Worker.cs?name=Worker)]

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

[!code-csharp[Startup](background-service/samples/2.2/Server/Worker.cs?name=Worker)]

::: moniker-end

As the `ExecuteAsync` method is called iteratively in the background service, the server's current date and time are sent to the connected clients using the `ClockHub`.

## React to SignalR events with background services

Like a Single Page App using the JavaScript client for SignalR, or a .NET desktop app using the <xref:signalr/dotnet-client>, a `BackgroundService` or `IHostedService` implementation can also be used to connect to SignalR Hubs and respond to events.

The `ClockHubClient` class implements both the `IClock` interface and the `IHostedService` interface. This way it can be enabled during `Startup` to run continuously and respond to Hub events from the server.

```csharp
public partial class ClockHubClient : IClock, IHostedService
{
}
```

During initialization, the `ClockHubClient` creates an instance of a `HubConnection` and enables the `IClock.ShowTime` method as the handler for the Hub's `ShowTime` event.

::: moniker range=">= aspnetcore-3.0"

[!code-csharp[The ClockHubClient constructor](background-service/samples/3.x/Clients.ConsoleTwo/ClockHubClient.cs?name=ClockHubClientCtor)]

In the `IHostedService.StartAsync` implementation, the `HubConnection` is started asynchronously.

[!code-csharp[StartAsync method](background-service/samples/3.x/Clients.ConsoleTwo/ClockHubClient.cs?name=StartAsync)]

During the `IHostedService.StopAsync` method, the `HubConnection` is disposed of asynchronously.

[!code-csharp[StopAsync method](background-service/samples/3.x/Clients.ConsoleTwo/ClockHubClient.cs?name=StopAsync)]

::: moniker-end
::: moniker range="<= aspnetcore-2.2"

[!code-csharp[The ClockHubClient constructor](background-service/samples/2.2/Clients.ConsoleTwo/ClockHubClient.cs?name=ClockHubClientCtor)]

In the `IHostedService.StartAsync` implementation, the `HubConnection` is started asynchronously.

[!code-csharp[StartAsync method](background-service/samples/2.2/Clients.ConsoleTwo/ClockHubClient.cs?name=StartAsync)]

During the `IHostedService.StopAsync` method, the `HubConnection` is disposed of asynchronously.

[!code-csharp[StopAsync method](background-service/samples/2.2/Clients.ConsoleTwo/ClockHubClient.cs?name=StopAsync)]

::: moniker-end

## Additional resources

* [Get started](xref:tutorials/signalr)
* [Hubs](xref:signalr/hubs)
* [Publish to Azure](xref:signalr/publish-to-azure-web-app)
* [Strongly typed Hubs](xref:signalr/hubs#strongly-typed-hubs)