Connection ID when calling SignalR Core Hub method from Controller

Question

This is a follow-up to another question and answer . What's the effect of calling HubContext.Clients.Caller or HubContext.Clients.Others from the controller? I see it depends on the connection ID . What value would it have in this situation?

If the connection ID (and thus Caller and Others ) is invalid then (from within the controller action) how could I obtain a connection ID (for the client currently calling the Web API) that I could use with HubContext.Clients 's methods?

Answer 1

What's the effect of calling HubContext.Clients.Caller or HubContext.Clients.Others from the controller? I see it depends on the connection ID. What value would it have in this situation?

There is neither .Caller nor .Others on HubContext.Clients (of type HubClients<THub> ).

" It's not possible to access those from IHubContext . Caller and Others both depend on knowing which client is the caller. When you're in IHubContext, we don't know and there may not even be a current caller since you could be in an MVC controller action, etc. "
— aspnet/SignalR#2274 (comment)

(from within the controller action) how could I obtain a connection ID (for the client currently calling the Web API) that I could use with HubContext.Clients 's methods?

" there is no way of knowing who the current caller is from the IHubContext "
— aspnet/SignalR#2274 (comment)

Using Groups and Users may be a solution

" If you have access to the User ID of the user who initiated the action, you can use .Users(userId) to send a message to all of that user's connections. Similarly, you add the SignalR connections to a group and send to that group using .Group(groupName) "
— aspnet/SignalR#2274 (comment)

Pass the connection ID from the client side

As of @microsoft/signalr 3.0.0, connectionId is available on HubConnection :

controller.doStuff(hubConnection.connectionId);

Outdated answer written at the time of @aspnet/signalr 1.0.0-rc1-update1:

You can get the connection ID on the client that calls the API, and then send it to the controller.

Hub:

 public string GetConnectionId() { return Context.ConnectionId; }

Client:

 connection.invoke('getConnectionId') .then(function (connectionId) { // Send the connectionId to controller controller.doStuff(connectionId); });