Core Python Programming (2nd Edition)

cs = socket() # create client socket
comm_loop: # communication loop
cs.sendto()/cs.recvfrom() # dialog (send/receive)
cs.close() # close client socket
Once a socket object is created, we enter the dialog loop of exchanging messages with the server. When
communication is complete, the socket is closed.
The real client code, tsUclnt.py, is presented in Example 16.4.
Example 16.4. UDP Timestamp Client (tsUclnt.py)
Creates a UDP client that prompts the user for messages to send to the server, gets them
back with a timestamp prefix, and displays them back to the user.
1 #!/usr/bin/env python
2
3 from socket import *
4
5 HOST = 'localhost'
6 PORT = 21567
7 BUFSIZ = 1024
8 ADDR = (HOST, PORT)
9
10 udpCliSock = socket(AF_INET, SOCK_DGRAM)
11
12 while True:
13 data = raw_input('> ')
14 if not data:
15 break
16 udpCliSock.sendto(data, ADDR)
17 data, ADDR = udpCliSock.recvfrom(BUFSIZ)
18 if not data:
19 break
20 print dataudpCliSock.close()
21
22 udpCliSock.close()
Line-by-Line Explanation
Lines 13
After the Unix startup line, we import all the attributes from the socket module, again, just like in the
TCP version of the client.
Lines 510
Because we are running the server on our local machine again, we use "localhost" and the same port
number on the client side, not to mention the same 1K buffer. We allocate our socket object in the same