[Question] [Serverless] How can I send a message to an individual client using REST API?

Dear Sirs,

I have studied the examples and I fully understand the architecture of Azure SignalR. I was able to broadcast messages from Postman. Also, I was able to run a chat example and was able to exchange messages.

The issue is: in a serverless scenario, how would I identify the id of an individual connected user? How Javascript clients can obtain their ID on Azure SignalR Service? This is needed because I want to send individual messages to a given user when his/her command gets processed on the backend. For example, in my use case, I would use a Azure Function to process a command that can take minutes to be executed.

What I have tried:

Using trace log on javascript client side, I was able to find an ID during negotiation:

Information: SSE connected to https://accendis-wefinance.service.signalr.net:5001/client/?hub=chat&id=61Ztvpa0KEQeKkJBgB2ZPQ&access_token=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYmYiOjE1MzEzNTY4OTcsImV4cCI6MTUzMTM1ODY5NywiaWF0IjoxNTMxMzU2ODk3LCJhdWQiOiJodHRwczovL2FjY2VuZGlzLXdlZmluYW5jZS5zZXJ2aWNlLnNpZ25hbHIubmV0OjUwMDEvY2xpZW50Lz9odWI9Y2hhdCJ9.NBFYcQaq-pl3c31AAeKmrLBIGnw-uON_MNWY0yMvJ_Y Utils.ts:165:20

So then I tried to build a new request using the id like this:

POST /api/v1-preview/hub/chat/user/61Ztvpa0KEQeKkJBgB2ZPQ HTTP/1.1
Host: accendis-wefinance.service.signalr.net:5002
Content-Type: application/json
Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJPbmxpbmUgSldUIEJ1aWxkZXIiLCJpYXQiOjE1MzEzMTgyMTUsImV4cCI6MTU2Mjg1OTQ5NCwiYXVkIjoiaHR0cHM6Ly9hY2NlbmRpcy13ZWZpbmFuY2Uuc2VydmljZS5zaWduYWxyLm5ldDo1MDAyL2FwaS92MS1wcmV2aWV3L2h1Yi9jaGF0L3VzZXIvNjFadHZwYTBLRVFlS2tKQmdCMlpQUSIsInN1YiI6IiJ9.aVhw0AyQ-WuT9NIymFzESn6Gv3R3zLedddqCngLzxFg
Cache-Control: no-cache
Postman-Token: 329b9cbd-8f86-4e62-8a3f-c5e23b8af025

{ "target": "newMessage0", "arguments": [ {
	"sender": "mario",
	"text": "API rest do SignalR"
} ] }

And as result, I receive a 202 but nothing happens on client side.

How can I see what really happened?

[mariomeyrelles]

Thanks @chenkennt

It works!

For sake of completeness, here is an example of token generation (negotiation) Azure Function in Javascript. Claims.NameIdentifier maps to sub in jwt:

var jwt = require('jsonwebtoken')

module.exports = function (context, req, connectionInfo) {

    var token = {
            "iss": "MyService",
            "aud": connectionInfo.endpoint,
            "sub": req.query.uid
    }
    var secret = process.env["AzureSignalRKey"];
    var signed = jwt.sign(token,secret, { expiresIn: '48h' });
    connectionInfo.accessKey = signed;
    context.res = { body: connectionInfo };
    context.done();
};

On the client, the negotiation and connection process can be done like this:

function getConnectionInfo() {
    return axios.post(`${apiBaseUrl}/api/SignalRInfo?uid=${data.username}`, null, getAxiosConfig())
        .then(resp => resp.data);
}
getConnectionInfo().then(info => {
const options = {
    accessTokenFactory: () => info.accessKey,
    logMessageContent: false
};
const connection = new signalR.HubConnectionBuilder()
    .withUrl(info.endpoint, options)
    .configureLogging(signalR.LogLevel.Trace)
    .build();
    
connection.on('newMessage', newMessage);
connection.onclose(() => console.log('disconnected'));
console.log('connecting...');

connection.start()
    .then((data) => console.log('connected!', data))
    .catch(console.error);
}).catch(console.error);

Thanks for your help again!

[shiweiwei114]

In this scenario what did you use for userId input binding on your negotiate Azure function?

I don’t think @mariomeyrelles is putting any userId to the input binding for SignalR service, he was generating the access token by himself and adding the userId as part of the token signature.