During this explosion of the internet of things; the things need care and feeding. Sure, sometimes they are small and every unimportant like a bot following a crayon line but then there are other cases where cash registers, scales, remote printers, wifi gateways, or your toaster needs a hug.
One such system I designed used ssh, bash, and a semaphore file. The amazing thing is that it scaled well when I used OpenBSD as the ssh server. I even designed it with HA in mind such that there were two ssh servers that the remote devices could connect to. One weakness that the system has is that it’s not on-demand. There is a cycle time between the device and the server.
(a) make a connection to the ‘a’ server and set the timeout
(b) if the timeout expired drop the connection
© make a connection to the ‘b’ server and set the timeout