Python udp broadcast client server example.

README.md

Python udp broadcast client-server example

⚠️ ❗ ATTENTION ❗ ⚠️

This gist is deprecated and will not be edited in the future. Consider visit ninedraft/python-udp repo. It will not be deleted, however.

⚠️ ❗ ATTENTION ❗ ⚠️

Works for python 3.7 and 2.7 for Mac OS and Linux(kernel>=3.9) hosts. If you'ra using linux(kernel<3.9), then use socket.O_REUSEADDR instead of socket.SO_REUSEPORT to share (host, port) between multiple clients and servers.

Tricks and traps:

• Socket portability issues: How do SO_REUSEADDR and SO_REUSEPORT differ?;
• Awesome "Socket Programming HOWTO";

client.py

import socket

client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP) # UDP

# Enable port reusage so we will be able to run multiple clients and servers on single (host, port). 
# Do not use socket.SO_REUSEADDR except you using linux(kernel<3.9): goto https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ for more information.
# For linux hosts all sockets that want to share the same address and port combination must belong to processes that share the same effective user ID!
# So, on linux(kernel>=3.9) you have to run multiple servers and clients under one user to share the same (host, port).
# Thanks to @stevenreddie
client.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

# Enable broadcasting mode
client.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

client.bind(("", 37020))
while True:
    # Thanks @seym45 for a fix
    data, addr = client.recvfrom(1024)
    print("received message: %s"%data)

server.py

import socket
import time

server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)

# Enable port reusage so we will be able to run multiple clients and servers on single (host, port). 
# Do not use socket.SO_REUSEADDR except you using linux(kernel<3.9): goto https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ for more information.
# For linux hosts all sockets that want to share the same address and port combination must belong to processes that share the same effective user ID!
# So, on linux(kernel>=3.9) you have to run multiple servers and clients under one user to share the same (host, port).
# Thanks to @stevenreddie
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

# Enable broadcasting mode
server.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

# Set a timeout so the socket does not block
# indefinitely when trying to receive data.
server.settimeout(0.2)
message = b"your very important message"
while True:
    server.sendto(message, ('<broadcast>', 37020))
    print("message sent!")
    time.sleep(1)

Thank you for offer the code. I was runing the server and client codes on a group of remote machines. I wrote a powershell script to SSH into the server and client machines to start the python codes.
It seems the python codes freezes/hang the SSH every time. May I ask what is causing that and if there is a way around it? Thanks!