Python send UDP packet

Question

I am trying to write a program to send UDP packets  as in  https   wiki python org moin UdpCommunication The code appears to be in Python 2   import socket  UDP IP    127 0 0 1  UDP PORT   5005 MESSAGE    Hello  World    print  UDP target IP    UDP IP print  UDP target port    UDP PORT print  message    MESSAGE  sock   socket socket socket AF INET    Internet              socket SOCK DGRAM    UDP sock sendto MESSAGE   UDP IP  UDP PORT     If I put parenthesis around the printed stuff  it just prints it on the screen   What do I need to do to make this work

User · Answer

Here is a complete example that has been tested with Python 2.7.5 on CentOS 7.

#!/usr/bin/python

import sys, socket

def main(args):
    ip = args[1]
    port = int(args[2])
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    file = 'sample.csv'

    fp = open(file, 'r')
    for line in fp:
        sock.sendto(line.encode('utf-8'), (ip, port))
    fp.close()

main(sys.argv)

The program reads a file, sample.csv from the current directory and sends each line in a separate UDP packet. If the program it were saved in a file named send-udp then one could run it by doing something like:

$ python send-udp 192.168.1.2 30088

User · Answer

Manoj answer above is correct  but another option is to use MESSAGE encode   or encode  utf-8   to convert to bytes  bytes and encode are mostly the same  encode is compatible with python 2  see here for more  full code   import socket  UDP IP    127 0 0 1  UDP PORT   5005 MESSAGE    Hello  World    print  UDP target IP   s    UDP IP  print  UDP target port   s    UDP PORT  print  message   s    MESSAGE   sock   socket socket socket AF INET    Internet                      socket SOCK DGRAM    UDP sock sendto MESSAGE encode     UDP IP  UDP PORT

User · Answer

Your code works as is for me  I m verifying this by using netcat on Linux   Using netcat  I can do nc -ul 127 0 0 1 5005 which will listen for packets at    IP  127 0 0 1 Port  5005 Protocol  UDP   That being said  here s the output that I see when I run your script  while having netcat running    9 34am  wlynch watermelon    nc -ul 127 0 0 1 5005 Hello  World

User · Answer

With Python3x  you need to convert your string to raw bytes  You would have to encode the string as bytes  Over the network you need to send bytes and not characters  You are right that this would work for Python 2x since in Python 2x  socket sendto on a socket takes a  plain  string and not bytes  Try this   print  UDP target IP    UDP IP  print  UDP target port    UDP PORT  print  message    MESSAGE   sock   socket socket socket AF INET  socket SOCK DGRAM    UDP sock sendto bytes MESSAGE   utf-8     UDP IP  UDP PORT

User · Answer

If you are running python 3 then you need to change the print statements to print functions  i e  put things in brackets    after print statements   The only thing that you will see the above do is the prints unless you have something listening on 127 0 0 1 port 5005 as you are sending a packet not receiving it - so you need to implement and start the other part of the example in another console window first so it is waiting for the message

[python] Python send UDP packet

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