ITraxTrainEventClient

The strongly typed client surface of the Trax SignalR hub. It names the one method the server calls on a connected client: TrainEvent, once per lifecycle event that passes the UseSignalRHub sink's filters. A client subscribes to that method name; it does not implement the interface.

Signature

namespace Trax.Effect.Broadcaster.SignalR.Services;
 
public interface ITraxTrainEventClient
{
    Task TrainEvent(object payload);
}
 
public sealed class TraxTrainEventHub : Hub<ITraxTrainEventClient>
{
    public TraxTrainEventHub();
}

Parameter	Type	Description
`payload`	`object`	The event as the sink's projection shaped it: a `TraxClientEvent` unless `WithProjection` replaced it

Returns: a task that completes when SignalR has handed the message to the transport.

The payload is object so a projection can produce any JSON-serializable shape without a generic parameter on the hub. Clients deserialize it themselves.

Receiving events

Client	Subscribe with
.NET (`Microsoft.AspNetCore.SignalR.Client`)	`connection.On<TraxClientEvent>("TrainEvent", handler)`, or your projection's type
JavaScript / TypeScript (`@microsoft/signalr`)	`connection.on("TrainEvent", handler)`

The hub is mapped with MapTraxTrainEventHub, at /hubs/trax-events by default; that page has complete client examples.

Example

var connection = new HubConnectionBuilder()
    .WithUrl("https://app.example.com/hubs/trax-events",
        o => o.AccessTokenProvider = () => tokens.GetAsync())
    .WithAutomaticReconnect()
    .Build();
 
connection.On<TraxClientEvent>("TrainEvent", evt =>
    Console.WriteLine($"{evt.TrainName} {evt.EventType} ({evt.ExternalId})"));
 
await connection.StartAsync();

Remarks

TraxTrainEventHub defines no methods a client can invoke. It only pushes.
Every client the hub admits receives every event that passes the sink's filters. The default TraxClientEvent leaves out the failure reason and output for that reason; see Default projection.

Package

dotnet add package Trax.Effect.Broadcaster.SignalR