Enable the webapp to launch commands in the host machine via a local webserver, of course in a credential-controlled way. The webapp in that mode may be set perpetually to manual sync, triggered by web-push notifications. The local webserver mentioned may then launch a @SomajitDey/tunnel or a free ngrok exposure for establishing remote sessions.

Basically, this mechanism avoids constant polling or keeping alive idle connections. Tunnels are launched / Remote commands are invoked just in time, as and when needed, triggered by a simple web-push!