How would you push a 'message' to a device using Node.js?

Question

Now here's a really weird question that I couldn't find the answer to on the internet. Here's how I'm planning to build a project: Controller App --> Node.js Server (probably Express) --> Some IoT Device Running Node.js Who Knows Where

So essentially, the Controller App wants to control an IoT device, but it could be anywhere. So, it communicates to a server which sits on a static IP which will keep track of where this IoT device is (could be on any network/IP/port). So the controller app will send a request to the server, and the server will tell this IoT device wherever it is to do something.

The problem is, how will this Node.js Server know where the device is?

Proposed Solution A: One way I thought of was to have a server, and share a secret string between the server and the IoT device. The server will have some 'endpoint(?)' that the IoT device can 'subscribe' to.

Proposed Solution B: The IoT device forms a WebSocket or a Sockets.io connection. Whilst this might be a better and easier solution, when you add many devices, will the server take up much more resources when it's communicating to multiple devices in real time?

So yeah, a really weird question, because here, it's really a push notification from Node.js -> Node.js, rather than what every other search result is about, for Node.js -> Some Notification Service like iOS or Google or Web Service Workers.

Thanks!

Answer 1

The "push" options are generally as follows:

1. Client polls an endpoint every once in a while to check if there's something new. Not really push, but very simple to implement. Feasability for using this implementation depends upon how "real-time" you need the push to be.

2. Client creates and maintains a constant connection with the server and the server can then send data over that connection at any time. This would be the webSocket or socket.io option or, in some cases SSE (server sent events) which is a version of continuous http. The client will need the ability to detect when the connection has dropped and re-establish the connection as needed. Obviously, the server needs the ability to handle a simultaneous connection (but mostly idle connection) from every device you're supporting. If the traffic is low, custom server configurations can support hundreds of thousands of connections. Typical shared hosting solutions are much more limited in this regard as they don't give you access to the whole server's resources.

3. Server uses some existing "push service" that is built into the client. This would work for an iOS or Android device that has a push service as part of the platform. Not available to a custom IoT device.

4. Third party push services or libraries. Google has Firebase Cloud Messaging which purports to be usable with IoT devices, but I'm mostly just finding examples of the IoT device initiating the event and having that event then pushed to more classic devices (phones, browsers, etc...), not from node.js server to IoT device.