In Feathers, realtime means that services automatically send created, updated, patched and removed events when a create, update, patch or remove service method is complete. Clients can listen for these events and then react accordingly.

With Feathers websockets aren't just used for sending events from server to client. It is also possible to call service methods and send data over sockets, either from server-to-server or client-to-server. This is often much faster than going through the REST API and results in a snappier app.

Currently Feathers supports two websocket transport libraries:

• Socket.io - Probably the most commonly used real-time library for NodeJS. It works on every platform, browser or device, focusing equally on reliability and speed.
• Primus - Is a universal wrapper for real-time frameworks that supports Engine.IO, WebSockets, Faye, BrowserChannel, SockJS and Socket.IO

In this chapter we will look at how to use Service events, how to configure the Socket.io and Primus real-time libraries and about how to restrict sending events to specific clients.