patchbay.pub is a free web service you can use to implement things like static site hosting, file sharing, cross-platform notifications, webhooks handling, smart home event routing, IoT reporting, job queues, chat systems, bots, etc, all completely serverless and requiring no account creation or authentication. Most implementations need nothing but curl and simple bash snippets.

WAMP is an open WebSocket subprotocol that provides two asynchronous messaging patterns: RPC and PubSub.