Can a SignalR Hub receive events from clients? And if so, how? - asp.net-core

Question

I have a signalR hub that needs to be able to receive an event from a client and then notify all other clients connected to the hub.
Is that possible?
I want my 'hub' application to be able to receive messages and send them. I can only figure out how to do the sending of messages. Here is what I have now:
Application 1-- Hub
Startup class:
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
services.AddSignalR().AddHubOptions<EventsHub>(options =>
{
options.HandshakeTimeout = TimeSpan.FromMinutes(5);
options.EnableDetailedErrors = true;
});
services.AddTransient(typeof(BusinessLogic.EventsBusinessLogic));
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
app.UseSignalR((configure) =>
{
configure.MapHub<EventsHub>("/hubs/events", (options) =>
{
});
});
}
Set Up of the Hub in Application 1
public class EventsHub : Hub
{
public EventsHub()
{
}
public override Task OnConnectedAsync()
{
if (UserHandler.ConnectedIds.Count == 0)
{
//Do something on connect
}
UserHandler.ConnectedIds.Add(Context.ConnectionId);
Console.WriteLine("Connection:");
return base.OnConnectedAsync();
}
public override async Task OnDisconnectedAsync(Exception exception)
{
//Do something on Disconnect
}
public static class UserHandler
{
public static HashSet<string> ConnectedIds = new HashSet<string>();
}
}
BusinessLogic:
public class EventsBusinessLogic
{
private readonly IHubContext<EventsHub> _eventsHub;
public EventsBusinessLogic(IHubContext<EventsHub> eventsHub)
{
_eventsHub = eventsHub;
}
public async Task<Task> EventReceivedNotification(ProjectMoonEventLog eventInformation)
{
try
{
await _eventsHub.Clients.All.SendAsync("NewEvent", SomeObject);
}
catch (Exception e)
{
throw new Exception(e.Message);
}
}
}
In the second application, that listens for events or messages from the hub:
Startup.cs
private static void ConfigureAppServices(IServiceCollection services, string Orale, string Sql)
{
services.Configure<CookiePolicyOptions>(options =>
{
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddOptions();
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
//set up of singletons and transients
services.AddHostedService<Events.EventingHubClient>();
}
The ClientHub to connect to application 1:
public class EventingHubClient : IHostedService
{
private HubConnection _connection;
public EventingHubClient()
{
_connection = new HubConnectionBuilder()
.WithUrl("http://localhost:61520/hubs/events")
.Build();
_connection.On<Event>("NewEvent",
data => _ = EventReceivedNotification(data));
}
public async Task<Task> EventReceivedNotification(Event eventInformation)
{
try
{
//Do something when the event happens
return Task.CompletedTask;
}
catch (Exception e)
{
throw new Exception(e.Message);
}
}
public async Task StartAsync(CancellationToken cancellationToken)
{
// Loop is here to wait until the server is running
while (true)
{
try
{
await _connection.StartAsync(cancellationToken);
Console.WriteLine("Connected");
break;
}
catch (Exception e)
{
Console.WriteLine(e.Message);
await Task.Delay(100);
}
}
}
public Task StopAsync(CancellationToken cancellationToken)
{
return _connection.DisposeAsync();
}
}
This works, but now I want application 2 to be able to send a message to application 1? So I need a similar piece of code as in the EventsBusinessLogic class in application2 to send messages to application 1.
I hope this is clear enough? Is this the purpose of SignalR?

Answer 1

Please refer to signalR documentation signalR documentation for .net client
I guess in your Hub method like this
public async Task SendTransaction(Transaction data)
{
await Clients.All.SendAsync("TransactionReceived", data);
}
Then add methods in client side
in constructor add
connection.On<Transaction>("TransactionReceived", (data) =>
{
this.Dispatcher.Invoke(() =>
{
var transactionData = data;
});
});
and then SendTransaction expected on server
private async void SendTransaction(Transaction data)
{
try
{
await connection.InvokeAsync("SendTransaction", data);
}
catch (Exception ex)
{
//
throw
}
}