WEBSOCKET TRONG NODEJS.

WebSocket is a protocol providing full-duplex communication channels over a single TCP connection. The WebSocket protocol was standardized by the IETF as RFC 6455 in 2011, and the WebSocket API in Web IDL is being standardized by the W3C.

WebSocket is designed to be implemented in web browsers and web servers, but it can be used by any client or server application. The WebSocket Protocol is an independent TCP-based protocol. Its only relationship to HTTP is that its handshake is interpreted by HTTP servers as an Upgrade request.[1] The WebSocket protocol makes more interaction between a browser and a website possible, facilitating live content and the creation of real-time games. This is made possible by providing a standardized way for the server to send content to the browser without being solicited by the client, and allowing for messages to be passed back and forth while keeping the connection open. In this way a two-way (bi-directional) ongoing conversation can take place between a browser and the server. The communications are done over TCP port number 80, which is of benefit for those environments which block non-web Internet connections using a firewall. Similar two-way browser-server communications have been achieved in non-standardized ways using stopgap technologies such as Comet.

The WebSocket protocol is currently supported in most major browsers including Google Chrome, Internet Explorer, Firefox, Safari and Opera. WebSocket also requires web applications on the server to support it.

Websocket được phân chia thành 3 mục sau:

1.    Protocal implementations : Nó tập trung vào high-performance và phục tùng các tiêu chuẩn của giao thức websocket: ws, faye-websocket, websocket

2.    Wesocket emulators: xây dựng trên sự thực thi giao thức bởi việc them các fallback vào tính năng websocket-like sử dụng việc truyền tải XHR long-polling hoặc htmlfile.Sự tồn tại những mô đun này phù hợp cho tính năng real time của trình duyệt hoặc các mạng hỗ trợ websocket: sockjs, engine.io,

3.    Có những mô đun cấp cao được xây dựng trên lớp emulator với sự tương thích như: broadcast message, channels, rooms và custom event emitters: socket.io , websocket-multiplex, shoe, primus.