---
title: Use MessagePack Hub Protocol in SignalR for ASP.NET Core
author: tdykstra
description: Add MessagePack Hub Protocol to ASP.NET Core SignalR.
monikerRange: '>= aspnetcore-2.1'
ms.author: tdykstra
ms.custom: mvc
ms.date: 06/04/2018
uid: signalr/messagepackhubprotocol
---

# Use MessagePack Hub Protocol in SignalR for ASP.NET Core

By [Brennan Conroy](https://github.com/BrennanConroy)

This article assumes the reader is familiar with the topics covered in [Get Started](xref:tutorials/signalr).

## What is MessagePack?

[MessagePack](https://msgpack.org/index.html) is a binary serialization format that is fast and compact. It's useful when performance and bandwidth are a concern because it creates smaller messages compared to [JSON](https://www.json.org/). Because it's a binary format, messages are unreadable when looking at network traces and logs unless the bytes are passed through a MessagePack parser. SignalR has built-in support for the MessagePack format, and provides APIs for the client and server to use.

## Configure MessagePack on the server

To enable the MessagePack Hub Protocol on the server, install the `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` package in your app. In the Startup.cs file add `AddMessagePackProtocol` to the `AddSignalR` call to enable MessagePack support on the server.

> [!NOTE]
> JSON is enabled by default. Adding MessagePack enables support for both JSON and MessagePack clients.

```csharp
services.AddSignalR()
    .AddMessagePackProtocol();
```

To customize how MessagePack will format your data, `AddMessagePackProtocol` takes a delegate for configuring options. In that delegate, the `FormatterResolvers` property can be used to configure MessagePack serialization options. For more information on how the resolvers work, visit the MessagePack library at [MessagePack-CSharp](https://github.com/neuecc/MessagePack-CSharp). Attributes can be used on the objects you want to serialize to define how they should be handled.

```csharp
services.AddSignalR()
    .AddMessagePackProtocol(options =>
    {
        options.FormatterResolvers = new List<MessagePack.IFormatterResolver>()
        {
            MessagePack.Resolvers.StandardResolver.Instance
        };
    });
```

## Configure MessagePack on the client

### .NET client

To enable MessagePack in the .NET Client, install the `Microsoft.AspNetCore.SignalR.Protocols.MessagePack` package and call `AddMessagePackProtocol` on `HubConnectionBuilder`.

```csharp
var hubConnection = new HubConnectionBuilder()
                        .WithUrl("/chatHub")
                        .AddMessagePackProtocol()
                        .Build();
```

> [!NOTE]
> This `AddMessagePackProtocol` call takes a delegate for configuring options just like the server.

### JavaScript client

MessagePack support for the Javascript client is provided by the `@aspnet/signalr-protocol-msgpack` NPM package.

```console
npm install @aspnet/signalr-protocol-msgpack
```

After installing the npm package, the module can be used directly via a JavaScript module loader or imported into the browser by referencing the *node_modules\\@aspnet\signalr-protocol-msgpack\dist\browser\signalr-protocol-msgpack.js* file. In a browser the `msgpack5` library must also be referenced. Use a `<script>` tag to create a reference. The library can be found at *node_modules\msgpack5\dist\msgpack5.js*.

> [!NOTE]
> When using the `<script>` element, the order is important. If *signalr-protocol-msgpack.js* is referenced before *msgpack5.js*, an error occurs when trying to connect with MessagePack. *signalr.js* is also required before *signalr-protocol-msgpack.js*.

```html
<script src="~/lib/signalr/signalr.js"></script>
<script src="~/lib/msgpack5/msgpack5.js"></script>
<script src="~/lib/signalr/signalr-protocol-msgpack.js"></script>
```

Adding `.withHubProtocol(new signalR.protocols.msgpack.MessagePackHubProtocol())` to the `HubConnectionBuilder` will configure the client to use the MessagePack protocol when connecting to a server.

```javascript
const connection = new signalR.HubConnectionBuilder()
    .withUrl("/chatHub")
    .withHubProtocol(new signalR.protocols.msgpack.MessagePackHubProtocol())
    .build();
```

> [!NOTE]
> At this time, there are no configuration options for the MessagePack protocol on the JavaScript client.

## Related resources

* [Get Started](xref:tutorials/signalr)
* [.NET client](xref:signalr/dotnet-client)
* [JavaScript client](xref:signalr/javascript-client)