WebSocket and Socket.IO - 401-advanced-javascript-jv/seattle-javascript-401d30 GitHub Wiki

WebSocket is a fast/close-to-realtime two-way communication method that runs on top of TCP, but much faster. It has a lot more features relating to reliability, which makes it easier to work with than basic TCP.

Socket.IO is a library that uses WebSockets to communicate, and which makes the whole process simple and streamlined. Socket.IO also adds more abilities on top of TCP, such as making namespaces and automatic connection.