Web Socket Hook is an open-source Sinatra-based service which bridges web hooks and web sockets. Now you can build apps that respond to web hooks even though your app may not be directly accessible from the internet. Using any standard web socket client you can connect to the WebSocketHook service, register a web hook, and receive messages via the web socket when the hook is called. Even in-browser JS or apps running behind a firewall can receive HTTP POSTs.