try socket

最小udp

参考了python的官方文档，写了最小的udp。

具体代码请点击：最小UDP

以上的代码有一些修改，不然会有一些坑，如图：

官方代码存在的问题在于，socket只listen一遍，导致不能重复listen

只要做出如下修改即可：

再理解UDP

错误

发现之前的代码是STREAM，属于TCP/IP协议。😓 所以也就是为什么TCP/IP协议要不停的去listen，对吗？

按照wp-lai的提示，找到了这篇文档：User Datagram Client and Server

Where TCP is a stream oriented protocol, ensuring that all of the data is transmitted in the right order, UDP is a message oriented protocol.

UDP does not require a long-lived connection, so setting up a UDP socket is a little simpler.

以下图是socket的运行机制

文档

从User Datagram Client and Server这篇文档里面搜集到一些比较关键的信息

Echo Server

Since there is no connection, per se, the server does not need to listen for and accept connections. It only needs to use bind() to associate its socket with a port, and then wait for individual messages.

Messages are read from the socket using recvfrom(), which returns the data as well as the address of the client from which it was sent.

Echo Client

The UDP echo client is similar the server, but does not use bind() to attach its socket to an address. It uses sendto() to deliver its message directly to the server, and recvfrom() to receive the response.