Author: Zen and the Art of Computer Programming
1 Introduction
The WebSocket protocol is a protocol for full-duplex communication between a web browser and a server. It is an application layer protocol built on top of TCP/IP and maintained by the IETF protocol standardization organization. The WebSocket protocol originally originated from Flash Socket, but was gradually extended to other programming environments. With the popularization of HTML5 technology, more and more websites begin to support the WebSocket protocol, such as chatting, games, stock quotes, real-time data transmission, etc.
The advantage of WebSocket is that it is lightweight and easy to use, because it only needs a TCP connection to communicate. And because of the binary frame format, there is no limit to the data size. But the disadvantage is also obvious, that is, it is more complicated to implement, and many details need to be considered. This article will deeply analyze the frame structure and implementation principle of the WebSocket protocol.
2. Explanation of basic concepts and terms
2.1 WebSocket protocol
The WebSocket protocol is an independent protocol that can run on top of HTTP, that is to say, the WebSocket protocol uses URIs to identify server resources. A WebSocket connection consists of two independent TCP connections, one is used to transmit data (real-time communication), and the other is used to send heartbeat packets to maintain the connection. Through this protocol, a reliable connection can be established between the client and the server.
The WebSocket protocol defines a series of opcodes and rules that are used to indicate the type of data stream, such as text data or binary data. It also defines a set of message formats, including handshake request and handshake response, notification of closing connection, ping/pong message and extension protocol.
2.2 Data frame
There are two types of data frames in the WebSocket protocol - text frame (text frame) and binary frame (binary fra