Chapter VIII of the socket network programming (3): What is a socket (socket)

TCP / UDP protocol is very complex, we can not all the time programming in-depth understanding, so this time there is a large cattle network programming procedures ape prepared a packaged module, program ape who call interface can be achieved as long as the network communication, no understanding of the principles of the agreement.

Socket abstraction layer
+ between the transport layer and application layer: the role is to make as long as the interaction with Socket Abstraction Layer application layer on it
+ the transport layer, the following functions (including transport layer) are all good package, leaving the interface to the program ape we use: the application layer directly call Socket abstraction layer interface on it

With Socket abstraction layer, we only use the Socket interface you can achieve the network programming.

Socket There are two families (Family):
+ based on file type: AF_UNIX
+ based network types: AF_INET

Socket-based workflow TCP work (simple example software):

server.py

import socket

#1 买手机
phone = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  # AF_INET是网络类型家族(基于网络通信),stream是流的意思,即TCP协议（流式协议）
# print(phone)

#2 绑定手机卡（绑定IP和端口）
phone.bind(('127.0.0.1',8080))  # 以元组的形式传入 服务端IP 和 接收端口
# IP需要设成服务器端的IP地址这里我们服务器和客户端都在本地，用本地回环IP：127.0.0.1
# 端口0-65535范围，其中0-1024是操作系统用的，其他的可以给我们的软件选用
# 注意：在重复运行软件的时候可能会报错，说端口已被占用。你可以换个端口，这时候客户端访问的端口也得换

#3 监听(设置最大可挂起数)
phone.listen(5)  # backlog:设置为5，最大挂起的连接数。类似电话占线，最多可以让5个人等待。这个值一般应该放在配置文件中

#4 等待呼叫（接受连接）
print('starting...')  
conn, client_addr = phone.accept()  # 服务器端会在这里等待客户端访问，返回的是2各元素的元组，所以我们分别赋值给conn和client_addr
# 被连接了会返回一个由 (连接对象,客户端IP&端口)组成的元组
# (<socket.socket fd=220, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=0, laddr=('127.0.0.1', 8080), raddr=('127.0.0.1', 1912)>, ('127.0.0.1', 1912))

#5 收,发消息(传数据)
# 使用连接对象来收，发消息
data = conn.recv(1024)  # recv是收,收1024字节：代表接受数据的最大1024bytes
print('客户端的数据',data)

conn.send(data.upper())  # 送回客户端数据

#6 挂电话(释放连接对象)
conn.close()  # 断开和此客户端的连接

#7 关机(关闭服务)
phone.close()  # 停止服务端的服务

# 服务端有2种套接字：phone，conn
# phone作用：绑定，监听，接受连接
# conn作用：收，发消息

client.py

import socket

#1 买手机
phone = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  # AF_INET是网络类型家族(基于网络通信),stream是流的意思,即TCP协议（流式协议）
 
# 客户端不需要绑定IP和端口

#2 拨号(发送请求)
phone.connect(('127.0.0.1',8080))  # 连接服务器的IP和端口

#3 发，收消息
phone.send('hello'.encode('utf-8'))  # 以前我们讲过，网络传输需要用bytes类型来传输
data = phone.recv(1024)
print(data)

#4 关闭
phone.close()

# 客户端只有1种套接字：发，收消息

Chapter VIII of the socket network programming (3): What is a socket (socket)

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