Original edition:

TCP is divided into client and server. Each server can only provide one download service for the client.

Improved version:

TCP is divided into client and server,

(1) each time the server can provide download service for the customer service terminal,

(2) the server can identify the nonexistent files and send them to the client,

(3) the client can exit the download service through the input, and the server can exit the service for the current client and wait for the service for the next client.

Difficulties:

(1) when processing non-existent files, the continue keyword is introduced. If not, when downloading non-existent files, the variables storing the data of the previous file will be sent to the client as data!!

(2) the client and server exit the current service and introduce the break keyword.

Self study and self practice, welcome to correct.

 1 # Client
 2 import socket
 3 
 4 def main():
 5 
 6     # 1,Create socket
 7 
 8     tcp_client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 9 
10 
11     # 2,Linked server
12     server_ip = input('Get server's IP:')
13     server_port = int(input('Get the port number of the server:'))
14     tcp_client.connect((server_ip, server_port))
15     print('reminder:')
16     print('*'*20)
17     print('If you want to terminate the download request, Please input " quit", Exit download!')
18     while True:   
19         # 3,Get the file name to download
20         file_name = input('Enter the file name to download:')
21         
22         
23 
24         # 4,Send filename to server
25         send_data = tcp_client.send(file_name.encode('utf-8'))
26         
27         if file_name == 'quit':
28             break
29         
30         # 5,receive data
31         recv_data = tcp_client.recv(1024)
32         if recv_data.decode('utf-8') != '101':
33             # print('Receiving data:' ,recv_data.decode('utf-8'))
34             with open('C:\\Users\\Administrator\\Desktop\\Trainee\\Network Communications\\'+ '[copy]'+file_name, 'wb') as f:
35                 f.write(recv_data)
36         else:
37             print('file does not exist')
38             
39     tcp_client.close()
40 
41 if __name__ == '__main__':
42     main()

 1 import socket
 2 def send_2_client(tcp_client, tcp_addr):
 3 
 4     # Loop to a client
 5     while True:    
 6     # 1 Receiving the file name data sent by the customer service terminal or receiving the request of the client to exit the download( quit)
 7         recv_data = tcp_client.recv(1024)
 8 
 9         file_name = recv_data.decode('utf-8')
10         print('Client:%s,Files requested to download:%s' % (str(tcp_addr),file_name))
11 
12     # Exit the download service for the current customer service terminal
13         if file_name == 'quit':
14             break
15     # 2 Read file data
16     
17         try:
18             f = open(file_name, 'rb')
19             send_content = f.read()
20             f.close()  #Close file, free memory
21         except:
22             print('file does not exist')
23             tcp_client.send('101'.encode('utf-8'))
24             continue #When the downloaded file does not exist, the cycle starts again, waiting for the client to send a new download request
25 
26     # 3 send data                
27         tcp_client.send(send_content)        
28     tcp_client.close()
29     
30 
31 
32 
33 
34 def main():
35     # 1,Create server socket
36     tcp_server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
37 
38     # 2,Binding address information
39     tcp_server_socket.bind(('', 7788))
40 
41     # 3,Set to passive listening
42     tcp_server_socket.listen(128)
43 
44     # 4,Loop waiting for client access
45     # Loop to multiple clients
46     while True:
47         print('Waiting for the access request of customer service terminal...')
48         tcp_client, tcp_addr = tcp_server_socket.accept()
49         send_2_client(tcp_client, tcp_addr)
50     tcp_server_socket.close()
51         
52         
53         
54             
55 if __name__ == '__main__':
56     main()