Q:

Signal from browser to desktop application

How then problem of sending signals (on some events) from web-site to desktop application (written on C#) can be solved? Which approaches you can recommend? Is WebSocket protocol is good for these goals?

A:

You can use Websockets from Javascript in HTML or poll the website for data using a HttpRequest object in C#.
I would recommend polling for data via HttpRequest since the data will be a little more reliable when not generated completely on the client machine.
Also you may use encryption methods for security.

