SignalR and Fiddler

ASP.NET SignalR is a library for pushing real-time updates from a web server to connected clients. During development, it can be useful to inspect the traffic between the server and clients using a tool like Fiddler.

Unfortunately, after the initial handshake, Fiddler shows very little:

Only the connection initialization is visible. Subsequent exchanges use WebSockets, which Fiddler does not intercept.

To work around this, disable WebSocket support in SignalR so it falls back to HTTP. Fiddler can then intercept and display all exchanges:

public void Configuration(IAppBuilder app)
{
    var transportManager = GlobalHost.DependencyResolver.Resolve<ITransportManager>() as TransportManager;
    if (transportManager != null)
    {
        transportManager.Remove("webSockets");
    }

    HubConfiguration hubConfiguration = new HubConfiguration();
    app.MapSignalR(hubConfiguration);
}

Here is the result:

Do you have a question or a suggestion about this post? Contact me!