Python - UDP client

Question

I am currently reading a Python book and came across the following example:

import socket
target_host = "127.0.0.1"
target_port = 80

# create a socket object
client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# send some data
client.sendto("AAABBBCCC",(target_host,target_port))

# receive some data
data, addr = client.recvfrom(4096)

print data

If I understood it right, I am building a listener to my own loop-back IP address on the UDP port 80. My question is, what is it good for and how I can "test" it? (Meaning how can I read the sent "AAABBBCCC")?

Thanks

Answer 1

You need to run a server to listen on the port your sender sent to. there is a good explanation here.

A nice example for you is (based on the above link):

import socket

UDP_IP = "127.0.0.1"
UDP_PORT = 80

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind((UDP_IP, UDP_PORT))

while True:
   data, addr = sock.recvfrom(1024) #buffer of 1024 bytes
   print "received message: ", data

You need to run the server first so it start listening and than run your client separately.

Answer 2

If you just want to validate the original server is working and don't need the destination server to be in python, netcat can do this really succinctly from the command line.

nc -ul 80