List of articles

• ** Connect to the server ：**
• • ** A simple server client program ：**
  • • ** The server **
    • ** client **

Socket programming is a method of connecting two nodes on a network to communicate with each other . A socket （ node ） Listen IP Specific port at , The other socket extends to the other socket to form a connection . The server forms a listener socket , The client connects to the server .
They are the real pillars behind Web browsing . Simply speaking , There is a server and a client .
Socket programming starts by importing the socket library and creating a simple socket .

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

ad locum , We made a socket instance , And pass it two parameters . The first parameter is zero AF_INET, The second parameter is SOCK_STREAM.AF_INET Refers to the address series ipv4.SOCK_STREAM Represents connection oriented TCP agreement .
Now? , We can use this socket to connect to the server .

Connect to the server ：

Please note that , If any error occurs during socket creation , Socket . Errors are thrown , We can only know its IP Connect to the server . You can use the following command to find the server's IP：

$ ping www.google.com

You can also use python find IP：

import socket
ip = socket.gethostbyname('www.google.com')
print(ip)

Output results ：

The following is for connecting to Google Example script for .

import socket
import sys
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print(" Successfully created socket ")
except socket.error as err:
print(" Socket creation failed , There is an error %s" % (err))
# Socket default port
port = 80
try:
host_ip = socket.gethostbyname('www.google.com')
except socket.gaierror:
print(" Error parsing host ")
sys.exit()
# Connect to the server
s.connect((host_ip, port))
print(" Socket successfully connected to google")

Running results ：

• First , We made a socket .
• Then we solved Google's IP, Last , We connect to Google .
• Now we need to know how to send some data through a socket .
• For sending data , The socket library has sendall function . This function allows you to send data to the server to which the socket is connected , And the server can also use this function to send data to the client .

A simple server client program ：

The server

The server has a bind（） Method , This method binds it to a specific IP And port , So that it can listen to the IP And incoming requests on the port . The server has a listen（） Method , It puts the server in listening mode . This allows the server to listen for incoming connections . Last , The server has a accept（） and close（） Method .accept Method to start the connection with the client ,close Method to close the connection with the client .

# First, import the socket font
import socket
# Next, create the socket object
s = socket.socket()
print (" Successfully created socket ")
# Keeping a port on your computer in our case is 12345, But it can be any port
port = 12345
# Next, bind to port , We didn't ip Field ip, Instead, you enter an empty string , This enables the server to listen for requests from other computers on the network
s.bind(('', port))
print (" The socket is bound to %s" %(port))
# Switch socket to listening mode
s.listen(5)
print (" Socket is listening ")
# A perpetual cycle , Until we interrupt it or something goes wrong
while True:
# Establish a connection with the client .
c, addr = s.accept()
print (' Got a connection from ', addr )
# Send a thank you message to the customer . Encode to send byte type .
c.send(' Thank you for your connection '.encode())
# Close connection to client
c.close()
# Break the cycle
break

• First , It is necessary for us to import sockets .
• Then we made a socket object , And in our PC A port is reserved on .
• after , We bind the server to the specified port . Passing an empty string means that the server can also listen for incoming connections from other computers . If we pass 127.0.0.1, Then it will listen only for those calls made on the local machine .
• 5 ad locum , We put the server in listening mode , This means that if the server is busy , be 5 Connections will be waiting , If the first 6 A socket tried to connect , Then the connection will be rejected .
• Last , We go through a cycle for a period of time , And start accepting all incoming connections , And close all connected sockets after sending a thank you message .

client

Now we need something that the server can interact with . We can believe in servers like this , Just to know that our server is working . Type the following command in the terminal ：

# Start the server
$ python server.py
# Keep the above terminals open
# Now open another terminal and type ：
$ telnet localhost 12345

If the following error is reported ：

You can click enable or disable... In the control panel windows Found in the function telent client And check the Click ok

Output ：

# # In the server .py Terminal you will see the following output ：
Successfully created socket
The socket is bound to 12345
Socket is listening
Got connection from ('127.0.0.1', 52617)

# stay telnet In the end , You will see ：
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Thank you for your connection .

This output shows that our server is working .
Now for the client ：

# Import socket modular
import socket
# Ships socket object
s = socket.socket()
# Define the port to be connected
port = 12345
# Connect to the server on the local computer
s.connect(('127.0.0.1', port))
# Receive data from the server and decode it to get a string .
print(s.recv(1024).decode())
# Close the connection
s.close()

• First , We make a socket object .
• then , We're at the port 12345（ Port on which the server is running ） Connect to localhost, Last , We receive data from the server and close the connection .
• Now save this file as client.py, And after starting the server script, run it from the terminal .

Running results ：