March 2022
Intermediate to advanced
522 pages
13h 52m
Chinese
Content preview from Python语言及其应用（第2版）
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292
第 17章
网络
时间是大自然阻止一切同时发生的方式。空间则阻止了一切发生在我身上。
——时间名言
在第
15
章中我们了解了
并发
：如何同时做多件事情。本章会尝试在不同的地方操作，即
分布式计算
或
联网
。挑战时间和空间的理由有很多。
性能
你的目标是让快速组件处于繁忙状态，而不是干等着慢速组件。
稳健性
数量越多就越保险，因此你希望利用重复的任务来应对软硬件故障。
简洁性
最好的方法是将复杂任务分解成多个易于确定、理解和修复的小任务。
可伸缩性
增加服务器数量以处理负载，减少服务器数量以节省内存。
本章会从联网原语讲起，直到高级概念。先从
TCP/IP
和套接字开始。
17.1 TCP/IP
互联网基于各种规则：如何创建连接、交换数据、终止连接、处理超时等。这些规则称为
协议
，以分层的方式组织在一起。分层的目的在于允许创新和出现替代方法。只要遵循上
层和下层的约定，你就可以在某一层中“为所欲为”。
网络
｜
293
最底层负责电子信号等方面，更高层以其下层作为基础。位于中间（基本上）的是
IP
（
Internet
protocol
，互联网协议）层，负责网络寻址以及分组（数据块）路由。在此之上，
有另外两个协议在负责传递数据。
UDP（user datagram protocol，用户数据报协议）
用于简短的数据交换。
数据报
是一次性发送的短消息，就像明信片上的便条。 ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.