How to get connection TransportType in SignalR Client?

Question

I have a Microsoft.AspNetCore.SignalR.Client based SignalR .NET Client.

Once a connection is established, I would like to determine what SignalR transport mechanism is being used for the connection for Debugging purposes. I am experiencing issues on a network and need to verify the current transport mechanism under various conditions.

A variety of questions similar to this have been asked:

• How to determine which transport method/protocol Azure SignalR is using?
• Determine transport method in SignalR Core?

But their answers are not working for me. As these questions are old (4 years), and that's in the period where SignalR had some deprecated packages and renaming. I am not certain they are relevant. They also appear to cover the server side transport type retrieval.

The core of their answer: Context.Features.Get<IHttpTransportFeature>().TransportType.ToString();

Is found within some function tests of SignalR, but once again this appears to be on the Server side, within a server side Hub.

How can this be done on the client side?

Answer 1

UPDATE

After investigating this issue in depth, we found that since HubConnectionBuilder does not expose methods that can directly access Transport, if we must implement it on the signalr client side, we need to encapsulate HubConnection ourselves to access Transport, but we will lose more advanced listening methods such as connection.on, which need to be rewritten by ourselves.

For the signalr client and server, the protocol for establishing a connection needs to be negotiated by both parties. The server's OnConnectedAsync method will definitely be executed, so I prefer the server to implement this function. You can choose to send it to the client side or not.

Here my sample.

Server side

public override async Task OnConnectedAsync()
{
    ...
    var transportType = Context.Features.Get<IHttpTransportFeature>()?.TransportType.ToString();

    await Clients.Caller.SendAsync("ReceiveTransportType", transportType);

    await base.OnConnectedAsync();
}

Client side

connection.On<string>("ReceiveTransportType", transportType =>
{
    Console.WriteLine($"Transport Type: {transportType}");
});

Since this view protocol is supposed to be used during the developer debugging phase, I don't think this method will affect performance.

---

After debugging and looking at the properties, I finally found the TransportType through the following GetTransportType method.

It is important to note that we must declare the protocol when connecting.

options.Transports = HttpTransportType.LongPolling;

If not declared, three protocols will be output by default.

using Microsoft.AspNetCore.Http.Connections;
using Microsoft.AspNetCore.SignalR.Client;
using System.Reflection;
using System.Text;

Console.OutputEncoding = Encoding.UTF8;
System.Console.OutputEncoding = System.Text.Encoding.UTF8;
//Console.WriteLine("Hello, World!");
// URL of the SignalR server
string url = "https://23p1z4dk-7189.euw.devtunnels.ms/mainhub?nickname=consoleapp1";

// Create connection
var connection = new HubConnectionBuilder()
    .WithUrl(url, options =>
    {
        options.Headers.Add("Authorization", "consoleapp1");
        options.Transports = HttpTransportType.LongPolling;
    })
    .Build();

// Connect to the server
try
{
    await connection.StartAsync();
    Console.WriteLine("Connection successful!");

    var transportType = Test.GetTransportType(connection);
    Console.WriteLine($"Transport type: {transportType}");
}
catch (Exception ex)
{
    Console.WriteLine($"Connection failed: {ex.Message}");
}

// Listen for messages from the server
connection.On<string>("ReceiveMessage", message =>
{
    Console.WriteLine($"Received message: {message}");
});

// Send a message to the server
await connection.InvokeAsync("SendMessage", "Hello from console app");

// Wait for user input to prevent console from closing
Console.WriteLine("Press any key to exit...");
Console.ReadKey();

// Close the connection
await connection.StopAsync();

public static class Test
{
    public static string GetTransportType(HubConnection connection)
    {
        // Get the _connectionFactory private field
        var connectionFactoryField = typeof(HubConnection).GetField("_connectionFactory", BindingFlags.NonPublic | BindingFlags.Instance);
        if (connectionFactoryField == null)
        {
            throw new InvalidOperationException("Could not find _connectionFactory field.");
        }

        var connectionFactoryValue = connectionFactoryField.GetValue(connection);

        // Get the _httpConnectionOptions private field
        var httpConnectionOptionsField = connectionFactoryValue.GetType().GetField("_httpConnectionOptions", BindingFlags.NonPublic | BindingFlags.Instance);
        if (httpConnectionOptionsField == null)
        {
            throw new InvalidOperationException("Could not find _httpConnectionOptions field.");
        }

        var httpConnectionOptionsValue = httpConnectionOptionsField.GetValue(connectionFactoryValue);

        // Get the Transports property
        var transportsProperty = httpConnectionOptionsValue.GetType().GetProperty("Transports", BindingFlags.Public | BindingFlags.Instance);
        if (transportsProperty == null)
        {
            throw new InvalidOperationException("Could not find Transports property.");
        }

        var transportsValue = (HttpTransportType)transportsProperty.GetValue(httpConnectionOptionsValue);

        return transportsValue.ToString();
    }
}