Socket

Sockets are an abstraction layer through which applications can send or receive data, open, read, write, and close like files.Sockets allow applications to plug I/O into the network and communicate with other applications on the network.A network socket is a combination of IP addresses and ports.

Development: Sockets were originally a network communication interface developed by the University of California, Berkely, for Unix systems.Later, with the development of TCP/IP network, sockets became the most common application interface and the most common API for application development on the Internet.

Application:

Realization:

Implement information exchange between Sever and Client based on TCP protocol

Sever side:

import socket
sk = socket.socket()            #Create a socket for the server
sk.bind(('127.0.0.1',8080))     #Bind Address to Socket

sk.listen()                     #Listen Link
conn,addr = sk.accept()         #Receive client connections and addresses
ret = conn.recv(1024)           #Receive client information
print(ret)                      #Print client information

conn.send(b'hi')                #Send information to client
conn.close()                    #Close client connections
sk.close()                      #Close Server Socket

Client side:

import socket
sk = socket.socket()             #Create Client Socket
sk.connect(('127.0.0.1',8080))   #Attempt to connect to server

sk.send(b'hello')                #Send message to server
ret = sk.recv(1024)              #Receive messages from the server
print(ret)                       #Print messages sent by the server

sk.close()                       #Close the client's socket

Sever side and Client side should receive and send information, not just receive or receive but execute Sever side before executing Client side.

Encountered a problem where the address was already in use when restarting the server

Solution:

How can clients and servers have multiple conversations?

Sever side:

import socket
from socket import SOL_SOCKET,SO_REUSEADDR
sk = socket.socket()            　　#Create a socket for the server
sk.setsockopt(SOL_SOCKET,SO_REUSEADDR,1)
sk.bind(('127.0.0.1',8080))     　　#Bind Address to Socket
sk.listen()                     　　#Listen Link
conn,addr = sk.accept()         　　#Receive client connections and addresses

print(addr)                     　　#Print client address
ret = conn.recv(1024)           　　#Receive client information
print(ret)                      　　#Print client information
conn.send(b'hi')                　　#Send information to client
print(addr)                     　　#Print client address
ret = conn.recv(1024)           　　#Receive client information
print(ret)                      　　#Print client information
conn.send(b'hi')                　　#Send information to client

conn.close()                    　　#Close client connections
sk.close()                      　　#Close Server Socket

Client side:

import socket
sk = socket.socket()                #Create Client Socket
sk.connect(('127.0.0.1',8080))      #Attempt to connect to server

sk.send(b'hello')                   #Send message to server
ret = sk.recv(1024)                 #Receive messages from the server
print(ret)                          #Print messages sent by the server
sk.send(b'hello')                   #Send message to server
ret = sk.recv(1024)                 #Receive messages from the server
print(ret)                          #Print messages sent by the server

sk.close()                          #Close the client's socket

Execution results:

So we can complete the process of sending and receiving messages all the time just by having the Sever end receive and send messages in a loop, and the Client end send and receive messages in a loop after connecting to the Sever end, but this process is a dead loop and we need to add some conditions to make it more perfect

Sever side:

import socket
import time
from json import dumps
from socket import SOL_SOCKET,SO_REUSEADDR
sk = socket.socket()                                                                    #Create a socket for the server
sk.setsockopt(SOL_SOCKET,SO_REUSEADDR,1)
sk.bind(('127.0.0.1',8080))                                                             #Bind Address to Socket
sk.listen()                                                                             #Listen Link
conn,addr = sk.accept()                                                                 #Receive client connections and addresses

while 1:
    ret = conn.recv(1024).decode('utf-8')                                               #Receive client information
    if ret.strip() == 'bye' or ret.strip() == 'bye'.capitalize():                       #Conditions for Jumping Out of Cycle
        conn.send(b'bye')                                                               #Send out bytes Type Bye
        print('Client has disconnected!')
        break
    print(time.asctime(time.localtime(time.time())) + ' ' +  dumps(addr) + ':' + ret)   #Format Print Message from Client
    sendInfo = input(time.asctime(time.localtime(time.time())) + ' <<<')
    conn.send(sendInfo.encode('utf-8'))                                                 #Send information to client

conn.close()                                                                            #Close client connections
sk.close()                                                                              #Close Server Socket

Client side:

import socket
import time
sk = socket.socket()                                                                #Create Client Socket
sk.connect(('127.0.0.1',8080))                                                      #Attempt to connect to server

while 1:
    sendInfo = input(time.asctime(time.localtime(time.time())) + ' <<<')
    sk.send(sendInfo.encode('utf-8'))                                               #Send message to server
    ret = sk.recv(1024).decode('utf-8')                                             #Receive messages from the server
    if ret.strip() == 'bye' or ret.strip() == 'bye'.capitalize():                   #Conditions for Jumping Out of Cycle
        sk.send(b'bye')                                                             #Send out bytes Type Bye
        print('Sever has disconnected!')
        break
    print(time.asctime(time.localtime(time.time())) + ' ["127.0.0.1", 8080]:' + ret)#Format messages from print servers

sk.close()                                                                          #Close the client's socket

Execution results:

Implement information exchange between Sever and Client based on UDP protocol

Implement simple messaging

Sever side:

import socket
sk = socket.socket(type=socket.SOCK_DGRAM)      #Create Server Socket
sk.bind(('127.0.0.1',8080))                     #Bind Server Socket

msg,addr = sk.recvfrom(1024)                    #Receive client information and address
print(msg.decode('utf-8'))                      #Decode and print the information passed by the client
sk.sendto(b'Hello client!',addr)                #take bytes Address to which type of information is sent to the client

sk.close()                                      #Close Server Socket

Client side:

import socket
sk = socket.socket(type=socket.SOCK_DGRAM)      #Create Client Socket
ip_port = ('127.0.0.1',8080)

sk.sendto(b'Hello sever!',ip_port)              #Client sends information
ret,addr = sk.recvfrom(1024)                    #Receive the address and information of the server
print(ret.decode('utf-8'))                      #Print received information

sk.close()                                      #Close Client Socket

Execution results:

 

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