Download files based on tcp, and the application of struct module.

A TCP-based download

Client:

from socket import *
import os
def main():
    tcp_socket = socket(AF_INET, SOCK_STREAM) #Create a socket tcp_ip 
    = input( " Please input ip: " )
    tcp_port = int(input( " Please enter the port: " )) #Receive the ip and port of the server with the input 
    tcp_socket.connect((tcp_ip, tcp_port)) #Connect to the server 
    file_name = input( " Please enter the name of the file to download: " ) #Enter the file name to be downloaded 
    tcp_socket.send(file_name.encode()) #Send the file name to the server 
    new_file = open(file_name, " wb " ) #Create an empty file 
    time = 0 #Used for calculation read The number of bytes to take 
    while True:
        mes = tcp_socket.recv(1024) #Receive the content returned by the server 
        if mes: #If the content is not empty, execute 
            new_file.write(mes.decode()) #Decode and write to the file 
            time += len(mes) #Calculate bytes 
        else :
             if time == 0: #If the number of bytes is empty, no content is received 
                new_file.close() #Close the file os.remove 
                (file_name) #Delete the file just created 
                print ( " Nothing you want Downloaded file " )
             else :
                 print ( "The file was downloaded successfully" ) #If the time has a value, the name file transfer is completed 
            break 
    tcp_socket.close() #Close the socket 
if  __name__ == ' __main__ ' :
 main()

Server:

import socket
 def file_deal(file_name): #Define a function to process the file the user asks to download 
    try :
        files = open(file_name, " rb " ) # binary read 
        mes = files.read()
     except :
         print ( " No such file " )
     else :
        files.close()
        return mes
def main():
    tcp_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) #Create a socket 
    tcp_socket.bind(( "" ,8080)) #Fixed port number 
    tcp_socket.listen(128) #Convert active socket to passive socket Connect, listen to the connected client 
    while True:
        client_socket,client_addr = tcp_socket.accept() #Use accept to get the sub-socket and the address of the client 
        file_name = client_socket.recv(4096) #Receive data from the client 
        mes = file_deal(file_name) #Call the function to process the file downloaded by the user 
        if mes : #If the file is not empty send 
            client_socket.send(mes)
        client_socket.close() #Close the sub-socket 
if  __name__ == " __main__ " :
    main()