why websocket over ajax

发布时间：2020-12-16 00:19:42 所属栏目：百科来源：网络整理

导读：To handle chat-related messaging,you could poll the server with Ajax. But to make this application as responsive as possible,you’ll avoid using traditional Ajax as a means to send messages. Ajax uses HTTP as a transport mechanism,and HTTP

To handle chat-related messaging,you could poll the server with Ajax. But to make
this application as responsive as possible,you’ll avoid using traditional Ajax as a means
to send messages. Ajax uses HTTP as a transport mechanism,and HTTP wasn’t
designed for real-time communication. When a message is sent using HTTP,a new
TCP/IP connection must be used. Opening and closing connections takes time,and
the size of the data transfer is larger because HTTP headers are sent on every request.
Instead of employing a solution reliant on HTTP,this application will prefer Web-
Socket (http://en.wikipedia.org/wiki/WebSocket),which was designed as a bidirec-
tional lightweight communications protocol to support real-time communication.
Since only HTML5-compliant browsers,for the most part,support WebSocket,the
application will leverage the popular Socket.IO library (http://socket.io/),which
provides a number of fallbacks,including the use of Flash,should using WebSocket
not be possible. Socket.IO handles fallback functionality transparently,requiring no
additional code or configuration.

From: Node.js in action

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