如何使用 python 通过 Internet 连接广播消息？

Question

I am currently looking for a way to broadcast a message to connected devices using a standard internet connection. I have written some code but I am kind of confused as to where to add a script that sends a message to devices such as laptops, androids, and ios devices. My code is:

# Send UDP broadcast packets

MYPORT = 50000

import sys, time
from socket import *

s = socket(AF_INET, SOCK_DGRAM)
s.bind(('', 0))
s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)

while 1:
    data = repr(time.time()) + '\n'
    s.sendto(data, ('<broadcast>', MYPORT))
    time.sleep(2)

Answer 1

Just a little mistake in your code. replace s.sendto(data, ('<broadcast>', MYPORT)) by s.sendto(data.encode(), ('<broadcast>', MYPORT)) and it works !

It's because sendto need a bytes-like object and not str

Answer 2

So again I'll iterate that I think its best you look into IPv4 and UDP and how they work. But I'll explain a little here and give some code.

UDP has to bind to a port on a device in order to be able to listen for messages. If my pc has ip of 192.168.0.2 and I have a laptop at 192.168.0.3 and i want to use udp then I would need to do this. First I would need to decide on a port to use. I'll use 50000.

PC (192.168.0.2)

from socket import *

# Create socket that can broadcast
s = socket(AF_INET, SOCK_DGRAM)
s.setsockopt(SOL_SOCKET, SO_BROADCAST, 1)

# Bind to '' meaning we will listen for any message from any IP
# Bind to port 50000 so we can get messages sent to that port
s.bind(('', 50000))

# I'll broadcast a message to all devices on the network that are listening on port 50000
# But I could broadcast to any port. My listen port and send port don't have to be the same.
s.sendto(b"test", ('<broadcast>', 50000))

Laptop (192.168.0.3)

from socket import *

# Create a socket that is bound to port 50000
s = socket(AF_INET, SOCK_DGRAM)
s.bind(('', 50000))

# Wait for a message to come in on port 50000, and print it
print(s.recvfrom(1024))