Htykuut

I have a question on webhook. I'm making some IoT device (an Arduino, for example) which controls my TV. The device is connecting to a router and owns a local IP address. In addition, I have a cloud server setup. To control the TV using my phone, all I can think of is to send a HTTP request to the server from the phone, saying "hey I want to turn on the TV." The server takes notes, and the next time (hopefully not very late after) the IoT device query the server for command, the server tells it that the mobile user wants to turn on the TV.

In order to implement this, the IoT device has to send HTTP request to the server very frequently, therefore consuming quite some battery energy. Recently I heard the idea of "Webhook", saying that instead of querying the server frequently, one can provide a URL to the server so that in case there is any command from the user (in this case, me on the mobile phone), the server can make an HTTP request to the client (in this case, the controlling device).

However, the problem for me is my controlling device only has a local IP, and without manually doing the port forwarding on the router, I don't know how it can own a URL accessable by another user not living in the same LAN. Is this achievable?

I also knew the "websocket" protocol but it seems to me that the server needs to maintain a TCP connection with every client. With little knowledge to it, I can tell whether it's more suitable for the task I described. (Potentially, there will be tens of thousands of users controlling their own TVs through one server on the cloud.)

Did I misunderstand the usage of webhook entirely? If not, how do we solve the local IP problem?

Thanks very much!