Q: Azure SignalR Service Upstream not delivering messages to an Azure Function App I have set up a SignalR Service account in Azure.
I have set this to Serverless.
I have set the Upstream URL to https://THE-NAME-OF-MY-FUNC-APP.azurewebsites.net/runtime/webhooks/signalr?code=THE-DEFAULT-KEY-FROM-FUNC-APP-APPKEYS_HOST_DEFAULT
This is documented here, under Rule Settings: https://learn.microsoft.com/en-us/azure/azure-signalr/concept-upstream#rule-settings
I have an AZ Functions App created in Node/TypeScript where I have a function that has a SignalRTrigger in and an SignalRMessages out. Consider the following function.
function.js
{
  "bindings": [
    {
      "type": "signalRTrigger",
      "name": "invocation",
      "hubName": "mailbox",
      "category": "messages",
      "event": "heartbeat",
      "connectionStringSetting": "AzureSignalRConnectionString",
      "parameterNames":[
        "mailboxId"
      ],
      "direction": "in"      
    },
    {
      "type": "signalR",
      "name": "signalRMessages",
      "hubName": "mailbox",
      "connectionStringSetting": "AzureSignalRConnectionString",
      "direction": "out"
    }
  ],
  "scriptFile": "../dist/heartbeat/index.js"
}

And the index.js
import { AzureFunction, Context } from "@azure/functions"

const heartbeatTrigger: AzureFunction = async function (context: Context, invocation: any): Promise<void> {
    context.log.info('Heartbeat function executed');
    let mbid = context.bindingData.mailboxId;

    // output a hearbeat received
    context.bindings.signalRMessages = [{
        "target": "heartbeatReceived",
        "arguments": [mbid]
    }];

};

export default heartbeatTrigger;

When I use the @aspnet/signalr client in a Vue app I can connect to the SignalR hub.
When I try to use myConnection.send('heartbeat', '123') I expect the above function to get called.
This is not happening. I do not seem to be able to fire the function.
Can someone please help?

A: I've spent days on this.
Finally came across this document on GitHub
https://github.com/Azure/azure-functions-signalrservice-extension/tree/master/samples/bidirectional-chat
THIS explains how to get it all working - the big piece was the key that needs to be used. Signalr_extension!
