[Answer]-How to communicate between client device and webserver?

Instead of hand coding sockets, I would suggest using HTTP with BASIC authentication to communicate between the device and the web server. You can uniquely assign an id/pwd to each device, and BASIC authentication is well supported by all web servers and client side libraries.

There are some security concerns with BASIC authentication even if you use HTTPS, but it maybe acceptable in your particular case here.

Maybe you could use SSH, with Fabric for instance. Here an example.