在SignalR Project外部调用Client方法

Question

I am having concerns about how to use SgnalR in the following scenario:

There is a non-hub service project that runs a time-consuming task periodically. The clients should be notified about the progress of the running task. After making some research, SignalR seemed to be the right choice for this purpose.

The problem is, I want the Service-Hub-Clients system to be as loosely-coupled as possible. So, I hosted the Hub in IIS and as a SignalR documentation suggests, added a reference to the Hub context in the outside project and called the client method:

    hubContext = GlobalHost.ConnectionManager.GetHubContext<TheHub>()
    hubContext.Clients.All.progress(n, i);

Client side:

    private void InitHub()
    {
        hubConnection = new HubConnection(ConfigurationManager.AppSettings["hubConnection"]);

        hubProxy = hubConnection.CreateHubProxy("TheHub");
        hubConnection.Start().Wait();
    }

    hubProxy.On<int, int>("progress", (total, done) =>
        {
            task1Bar.Invoke(t => t.Maximum = total);
            task1Bar.Invoke(t => t.Value = done);
        });

On the client side the method isn't being invoked and after two days of research I can't get it working, although when making a call from the Hub itself, it works fine. I suspect I'm missing some configuration

Answer 1

You can't use the GlobalHost.Connection manager in your Hub class or service, if the caller is going to be any project other than the Web project.

GlobalHost.ConnectionManager.GetHubContext<TheHub>()

You should instead create a service class that would abstract the hub from the callers. The service class should have something like:

// This method is what the caller sees, and abstracts the communication with the Hub
public void NotifyGroup(string groupName, string message)
{
  Execute("NotifyGroup", groupName, message);
}

// This is the method that calls the Hub
private void Execute(string methodName, params object[] parameters)
{
  using (var connection = new HubConnection("http://localhost/"))
  {
    _myHub = connection.CreateHubProxy("TheHub");
    connection.Start().Wait();
    _myHub.Invoke(methodName, parameters);
    connection.Stop();
  }
}

The last bit which is the hub itself, should be something like:

public void NotifyGroup(string groupName, string message)
{
  var group = Clients.Group(groupName);
  if (group == null)
  {
    Log.IfWarn(() => $"Group '{groupName}' is not registered");
    return;
  }
  group.NotifyGroup(message);
}