Python server programming: Detailed explanation of how Socket works

Python is a popular dynamic programming language that is widely used in the field of Internet application development. In server-side programming, Python is also widely used, among which Socket programming is an important part of Python server programming.

This article will explore in detail the operating principle of Socket in Python and help readers understand how Python server programming is implemented.

1. What is Socket?

First of all, we need to clarify what Socket is. Sockets are a set of APIs between applications and network protocols. They specify how applications access the network and how the network transmits data.

Socket is an inter-process communication mechanism that can transmit data from one computer to another over the network. Socket programming is actually the process in which the program communicates with the network through the Socket API.

In Python, we can use the socket module to implement Socket programming. This module provides a series of interfaces and methods to facilitate us to create Socket servers and clients.

2. Python Socket programming process

Python Socket programming process is as follows:

1. Create a Socket object and determine the Socket type and protocol.
2. Bind IP address and port number.
3. Listen to client connection requests.
4. Accept client requests and return connection objects.
5. Data transmission and communication are performed through connection objects.

Below we will introduce in detail how to implement each step.

1. Create Socket Object

In Python, we can use the socket() function in the socket module to create a Socket object. This function requires two parameters, the first parameter is the Socket type, and the second parameter is the protocol used by the Socket.

The Socket type can be SOCK_STREAM (streaming Socket) or SOCK_DGRAM (datagram Socket). The streaming Socket means that the data transmitted through the network is a continuous data stream, while the datagram Socket means that the data is transmitted through the network. The transmitted data is in individual packets.

The protocol can be IPV4 or IPV6, for example: socket.AF_INET means using the IPV4 protocol, socket.AF_INET6 means using the IPV6 protocol.

The following is an example of creating a TCP/IP Socket:

import socket

server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

2. Bind IP address and port number

After creating the Socket object, we It needs to be bound to the specified IP address and port number. Use the bind() function to implement:

server_socket.bind(('localhost', 8888))

Among them, 'localhost' means binding to the local IP address, and 8888 means the specified port number.

3. Listen to client connection requests

After completing Socket binding, we need to use the listen() function to monitor client connection requests. The parameter of this function is the number of connections to wait for.

server_socket.listen(5)

The above code indicates that the server can wait for 5 connection requests at the same time.

4. Accept client requests and return connection objects

Use the accept() function to accept client connection requests and return connection objects and client address information.

conn, addr = server_socket.accept()

Among them, conn is the connection object, which can use the send() and recv() functions to realize data transmission and communication, and addr is the IP address and port number of the client.

5. Data transmission and communication through connection objects

After obtaining the connection object, we can use the send() and recv() functions for data transmission and communication .

On the server side, we can use the send() function to send data to the client and the recv() function to receive data from the client.

Example:

conn.send("Welcome to my server".encode())

data = conn.recv(1024).decode()
print('收到的数据是', data)

On the client side, we can use the send() function to send data to the server and the recv() function to receive data from the server.

Example:

client_socket.send("Hello, Server".encode())

data = client_socket.recv(1024).decode()
print('收到的数据是', data)

3. Commonly used methods in Socket programming

In Python Socket programming, the commonly used methods are as follows:

1. send(data): Send data to the other end of the connection. Data is the data sent, which can be a string or byte stream.
2. recv(buffer): Receive data sent by the other end of the connection. Buffer is the buffer size of the received data, usually 1024 bytes.
3. bind(address): Bind IP address and port. Address is a tuple, including IP address and port number.
4. listen(backlog): Start listening for connections, backlog is the number of waiting connections.
5. accept(): Accept the client connection request and return the connection object and client address information.
6. connect(address): Connect to the specified server address. Address is also a tuple, including the IP address and port number.

4. Summary

This article introduces in detail the operating principle of Socket in Python Socket programming, as well as the basic process and common methods of Socket programming. By in-depth understanding of the concept and programming implementation of Socket, readers can better master Python server-side programming technology.

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