Learn python from scratch with me (2) Network programming

foreword

Yesterday I explained the first time about getting started with python from scratch, and the compulsory content of programming grammar, such as getting started with python3, lists and tuples, strings, dictionaries, conditions, loops and other statements, functions, object-oriented, exceptions and file processing
1 .Learn python from scratch with me (1) Compulsory programming grammar

Today I will talk about the second part: python concurrent programming: network programming

This series of articles is based on the following learning route. Due to the large content: learning python from scratch to advanced advanced roadmap

Pay attention to the official account: python technology training camp , learn advanced step by step

Python resources suitable for zero-based learning and advanced people:

① Tencent certified python complete project practical tutorial notes PDF
② More than a dozen major manufacturers python interview topic PDF
③ Python full set of video tutorials (zero foundation-advanced advanced JS reverse)
④ Hundreds of project actual combat + source code + notes
⑤ Programming grammar - machine learning -Full-stack development-data analysis-crawler-APP reverse engineering and other full set of projects + documents
⑥ Exchange and study
⑦ Want to take part-time orders

Chapter 1: Network Programming

1. Network programming

Network programming refers to programming techniques that use computer networks for communication. In Python, socketnetwork programming can be implemented using modules.

socketIt is a network programming library that encapsulates TCP/IPthe protocol, which provides a general network programming interface that can be used to create client and server programs. In Python, you use socketmodules to create socketobjects and then use that object for network communication.

The following is a simple network programming example, in which a server and a client are created, the client sends a message to the server, and the server prints out the message after receiving it:

Server side code:

import socket

# 创建socket对象
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 绑定IP地址和端口号
server_socket.bind(('127.0.0.1', 8888))

# 监听端口
server_socket.listen(5)

print('服务器已启动，等待客户端连接...')

# 等待客户端连接
client_socket, client_address = server_socket.accept()

print('客户端已连接，地址为：', client_address)

# 接收客户端消息
data = client_socket.recv(1024)

print('接收到客户端消息：', data.decode())

# 关闭socket连接
client_socket.close()
server_socket.close()

Client code:

import socket

# 创建socket对象
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 连接服务器
client_socket.connect(('127.0.0.1', 8888))

# 发送消息
client_socket.send('Hello, server!'.encode())

# 关闭socket连接
client_socket.close()

PyCharmTo compile and run Matlabfiles in , you need to install Matlaband configure environment variables first. Then, PyCharmopen Matlabthe file in , click the run button to compile and run Matlabthe file. If parameters need to be passed, they can be set in the run configuration.

2. Introduction to TCP/IP

TCP/IPIt is a network protocol, which is the basic protocol of the Internet. TCP/IPThe protocol family includes many protocols, the most important of which is TCPthe and IPprotocol.

TCPThe protocol is a connection-oriented protocol that provides reliable data transmission services. TCPThe protocol establishes a connection through a three-way handshake, and then ensures reliable data transmission through data segmentation and confirmation mechanisms.

IPThe protocol is a connectionless protocol that provides data packet transmission services. The IP protocol determines the transmission path of the data packet through the routing algorithm, and then transmits the data packet to the destination.

In network programming, we usually use TCPprotocols for data transmission. TCPThe protocol provides reliable data transmission services, and is suitable for scenarios that need to ensure the reliability of data transmission, such as file transmission and mail transmission. The protocol IPis suitable for scenarios that require fast data transmission, such as video streaming, real-time communication, etc.

3. Network Design Module

1. Introduction to Socket

SocketIs a communication mechanism that allows different processes to communicate over a network. In Python, Socketthis is socketachieved through modules. SocketTypically used for communication between clients and servers, but can also be used for communication between processes.

2. Socket module use

Modules in Python socketprovide a set of functions and classes for creation and manipulation Socket. Commonly used functions and classes include:

• socket(): Create a Socket object.
• bind(): Bind the Socket to a specific address and port.
• listen(): Start listening for connection requests.
• accept(): Accept a connection request and return a new Socket object.
• connect(): Connect to a remote Socket.
• send():send data.
• recv():Receive data.

3. Server

In Python, you can use socketmodules to create a server. A server usually needs to bind to a specific address and port and listen for connection requests. When a client connects to the server, the server accepts the connection request and creates a new Socketobject to handle the client request.

Here is a simple Python server example:

import socket

HOST = '127.0.0.1'  # 服务器地址
PORT = 8888  # 服务器端口号

# 创建一个Socket对象
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 绑定到地址和端口
server_socket.bind((HOST, PORT))

# 开始监听连接请求
server_socket.listen(1)

print('Server is running on {}:{}'.format(HOST, PORT))

while True:
    # 接受一个连接请求，并返回一个新的Socket对象
    client_socket, client_address = server_socket.accept()
    print('Client connected from {}:{}'.format(client_address[0], client_address[1]))

    # 处理客户端请求
    data = client_socket.recv(1024)
    print('Received data: {}'.format(data.decode()))

    # 发送响应数据
    response = 'Hello, client!'
    client_socket.send(response.encode())

    # 关闭连接
    client_socket.close()

4. Client

In Python, socketa client can be created using a module. Clients usually need to connect to a remote Socketand send request data. When the server responds to the request, the client receives the response data.

Here is a simple Python client example:

import socket

HOST = '127.0.0.1'  # 服务器地址
PORT = 8888  # 服务器端口号

# 创建一个Socket对象
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 连接到远程Socket
client_socket.connect((HOST, PORT))

# 发送请求数据
request = 'Hello, server!'
client_socket.send(request.encode())

# 接收响应数据
response = client_socket.recv(1024)
print('Received data: {}'.format(response.decode()))

# 关闭连接
client_socket.close()

5. File Downloader

A file downloader is a common web application that downloads files from a remote server and saves them locally. In Python, file downloaders can be implemented using socketmodules and modules.urllib

Here is a simple Python file downloader example:

import socket
import urllib.request

HOST = '127.0.0.1'  # 服务器地址
PORT = 8888  # 服务器端口号
FILE_URL = 'http://example.com/file.txt'  # 文件下载地址
FILE_NAME = 'file.txt'  # 文件保存路径

# 创建一个Socket对象
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# 连接到远程Socket
client_socket.connect((HOST, PORT))

# 发送请求数据
request = 'GET {}\r\n'.format(FILE_URL)
client_socket.send(request.encode())

# 接收响应数据
response = client_socket.recv(1024)
print('Received data: {}'.format(response.decode()))

# 下载文件并保存到本地
with open(FILE_NAME, 'wb') as f:
    while True:
        data = client_socket.recv(1024)
        if not data:
            break
        f.write(data)

# 关闭连接
client_socket.close()

4. Supplementary content

1. UDP protocol in network programming

UDP (User Datagram Protocol) is a connectionless and unreliable transmission protocol. It does not guarantee the reliability and sequence of data packets, but the transmission speed is fast, and it is suitable for some application scenarios that do not require high data reliability. Such as video, audio and other real-time transmission.

In Python, network programming of protocols socketcan be implemented using modules UDP. Here is an example of a simple UDPserver and client:

UDPserver:

import socket

# 创建UDP套接字
server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# 绑定IP地址和端口号
server_socket.bind(('127.0.0.1', 8888))

while True:
    # 接收数据
    data, addr = server_socket.recvfrom(1024)
    print('Received from %s:%s.' % addr)
    print('Data: %s' % data.decode())

    # 发送数据
    server_socket.sendto('Hello, client!'.encode(), addr)

UDPclient:

import socket

# 创建UDP套接字
client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# 发送数据
client_socket.sendto('Hello, server!'.encode(), ('127.0.0.1', 8888))

# 接收数据
data, addr = client_socket.recvfrom(1024)
print('Received from %s:%s.' % addr)
print('Data: %s' % data.decode())

# 关闭套接字
client_socket.close()

In UDPthe protocol, the destination address and port number need to be specified when sending data, and the address and port number of the sender will be returned when receiving data. Since UDPthe protocol does not guarantee the reliability and sequence of data, problems such as data loss, duplication, and disorder need to be considered in practical applications.

2. The difference between UDP protocol and TCP protocol

UDPProtocol and TCPprotocol are two commonly used network transmission protocols, and they have the following differences:

• Connection mode : TCPThe protocol is a connection-oriented protocol, while UDPthe protocol is a connectionless protocol. TCPProtocols require a connection to be established before transferring data, while UDPprotocols do not.

• Reliability : TCPThe protocol is a reliable protocol, which guarantees the reliable transmission of data, while UDPthe protocol is an unreliable protocol, which does not guarantee the reliable transmission of data.

• Transmission efficiency : UDPThe protocol TCPis more efficient than the protocol transmission, because UDPthe protocol does not need to establish a connection and maintain the connection state, but TCPthe protocol does.

• Packet size : UDPThe packet size of the protocol transmission is limited to 64KB, while TCPthe protocol has no limit.

• Application scenarios : TCPThe protocol is suitable for scenarios that require high reliability of data transmission, such as file transfer, email transmission, etc.; and the UDPprotocol is suitable for scenarios that require high real-time data transmission, such as live video broadcasting, voice calls, etc.

3. UDP protocol code implementation

UDPThe protocol is a connectionless protocol, which does not guarantee the reliability and sequence of data transmission, but has the advantage of fast transmission speed. UDPThe following is the code implementation of network programming using protocols in Python :

Server side code:

import socket

# 创建UDP套接字
server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# 绑定IP地址和端口号
server_socket.bind(('127.0.0.1', 8888))

# 接收数据
while True:
    data, addr = server_socket.recvfrom(1024)
    print('Received from %s:%s.' % addr)
    print('Data: %s' % data.decode())

    # 发送数据
    server_socket.sendto('Hello, client!'.encode(), addr)

Client code:

import socket

# 创建UDP套接字
client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# 发送数据
client_socket.sendto('Hello, server!'.encode(), ('127.0.0.1', 8888))

# 接收数据
data, addr = client_socket.recvfrom(1024)
print('Received from %s:%s.' % addr)
print('Data: %s' % data.decode())

# 关闭套接字
client_socket.close()

In the above code, the server first creates a UDPsocket and binds IPthe address and port number. Then recvfrom()receive the data sent by the client through the method, and sendto()send the data to the client through the method. The client also creates a UDPsocket, and sendto()sends data to the server through the method, and then recvfrom()receives the data sent by the server through the method. Finally, the client closes the socket.

This series of articles is based on the following learning route. Due to the large content: learning python from scratch to advanced advanced roadmap

Pay attention to the official account: python technology training camp , learn advanced step by step

Python resources suitable for zero-based learning and advanced people:

① Tencent certified python complete project practical tutorial notes PDF
② More than a dozen major manufacturers python interview topic PDF
③ Python full set of video tutorials (zero foundation-advanced advanced JS reverse)
④ Hundreds of project actual combat + source code + notes
⑤ Programming grammar - machine learning -Full-stack development-data analysis-crawler-APP reverse engineering and other full set of projects + documents
⑥ Exchange and study
⑦ Want to take part-time orders

The next chapter is about: python concurrent programming: multithreading