UDP sender and receiver in CircuitPython

udp_recv_code.py

# udp_recv_code.py -- receive UDP messages from any receiver, can be another CircuitPython device
# 24 Aug 2022 - @todbot / Tod Kurt
# cribbing from code at https://github.com/adafruit/circuitpython/blob/main/tests/circuitpython-manual/socketpool/datagram/ntp.py

import time, wifi, socketpool
from secrets import secrets
print("Connecting to WiFi...")
wifi.radio.connect(ssid=secrets['ssid'],password=secrets['password'])
print("my IP addr:", wifi.radio.ipv4_address)
pool = socketpool.SocketPool(wifi.radio)

udp_host = str(wifi.radio.ipv4_address) # my LAN IP as a string
udp_port = 5005             # a number of your choosing, should be 1024-65000
udp_buffer = bytearray(64)  # stores our incoming packet

sock = pool.socket(pool.AF_INET, pool.SOCK_DGRAM) # UDP socket
sock.bind((udp_host, udp_port))  # say we want to listen on this host,port

print("waiting for packets on",udp_host, udp_port)
while True:
    size, addr = sock.recvfrom_into(udp_buffer)
    msg = udp_buffer.decode('utf-8')  # assume a string, so convert from bytearray
    print(f"Received message from {addr[0]}:", msg)

udp_send_code.py

# udp_send_code.py -- send UDP messages to specified receiver, can be another CircuitPython device
# 24 Aug 2022 - @todbot / Tod Kurt
# cribbing from code at https://github.com/adafruit/circuitpython/blob/main/tests/circuitpython-manual/socketpool/datagram/ntp.py

import time, wifi, socketpool
from secrets import secrets
print("Connecting to WiFi...")
wifi.radio.connect(ssid=secrets['ssid'],password=secrets['password'])
print("my IP addr:", wifi.radio.ipv4_address)
pool = socketpool.SocketPool(wifi.radio)

udp_host = "192.168.1.123"  # LAN IP of UDP receiver
udp_port = 5005             # must match receiver!

my_message = "hi there from CircuitPython!"

sock = pool.socket(pool.AF_INET, pool.SOCK_DGRAM) # UDP, and we'l reuse it each time

num = 0
while True:
    # stick a nubmer on the end of the message to show progress and conver to bytearray
    udp_message = bytes(f"{my_message} {num}", 'utf-8')
    num += 1
    print(f"Sending to {udp_host}:{udp_port} message:", udp_message)
    sock.sendto(udp_message, (udp_host,udp_port) )  # send UDP packet to udp_host:port
    time.sleep(1)

OK, I'll will use a simple script to test. I already set port triggers in the router of my ISP. In the MS Windows 11 desktop PC running the X-Plane flight simulator I created UDP input/output rules for the ports needed in the Defender Firewall.

I used your receiver example (only modified to use settings.toml instead of the former secrets.py.
Script used:

# udp_recv_code.py -- receive UDP messages from any receiver, can be another CircuitPython device
# 24 Aug 2022 - @todbot / Tod Kurt
# cribbing from code at https://github.com/adafruit/circuitpython/blob/main/tests/circuitpython-manual/socketpool/datagram/ntp.py

import time, wifi, socketpool, os
print("Connecting to WiFi...")
wifi.radio.connect(ssid=os.getenv("CIRCUITPY_WIFI_SSID"), password=os.getenv("CIRCUITPY_WIFI_PASSWORD"))
print("my IP addr:", wifi.radio.ipv4_address)
pool = socketpool.SocketPool(wifi.radio)

# I, @PaulskPt, used for udp_host erroneously: os.getenv("MULTICAST_GROUP")
udp_host = str(wifi.radio.ipv4_address) # my LAN IP as a string  
udp_port = int(os.getenv("MULTICAST_PORT"))  # a number of your choosing, should be 1024-65000
udp_buffer = bytearray(64)  # stores our incoming packet

sock = pool.socket(pool.AF_INET, pool.SOCK_DGRAM) # UDP socket
sock.bind((udp_host, udp_port))  # say we want to listen on this host,port

print("waiting for packets on",udp_host, udp_port)
while True:
    size, addr = sock.recvfrom_into(udp_buffer)
    msg = udp_buffer.decode('utf-8')  # assume a string, so convert from bytearray
    print(f"Received message from {addr[0]}:", msg)

Resulting in the following output:

Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XGPS2,-85.700840,38.354860,156.1102,147.9949,0.0001,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0
Received message from 192.168.1.96: XATT2,148.0,5.9,0.5,-0.0000,0.0000,-0.0000,0.0,-0.0,-0.0,-0.01,0

Btw: the data is from a situation when the airplane was on the ground, parked. Engine running.

There is no packet reception when I use port 49707 or 49003 instead of port 49002.
Port 49707 is used for UDP datagrams (BECN and DATA packets) to Multicast group '169.255.1.1'. The DATA packets contain
data elements that I selected inside the X-Plane 12 setup

Update:
I receive the DATA packets when I enter in X-Plane settings for 'General Data Output' IP Address, the IP address: 192.168.1.110, which is the IP Address of the CPY device running the script, and Port 49707. But I get a 'UnicodeError' because the received UDP packets are packed.
When I modify the line 'msg = udp_buffer.decode('utf-8')' into: 'msg = udp.buffer' then the following output is received (only one packet copied below):

Received message from 192.168.1.96: bytearray(b'DATA*\x03\x00\x00\x00\x00\x00\x00\x00:\xb9\x989\xa9\xdf\x999\xd5E\x979\x00\xc0y\xc4\x00\x00\x00\x00\x1d\x13\xb19\xe5\x14\xae9\x11\x00\x00\x00e\xc6\xbc@8\xb5\t?\x1e\xff\x13C\x00\xc0y\xc4\xcb\x10\x19')

So, I think my problem is solved!
Again thank you for your rapid responses!

Thanks, this is very helpful!

By the way, line 22 of udp_recv_code.py

msg = udp_buffer.decode('utf-8')

should be

msg = udp_buffer[:size].decode('utf-8')

or otherwise you might print unwanted things:)

@aceg00 thank you for your response and advice.

@todbot You should consider updating this with the above correction from @aceg00 . The current code is a real foot gun. Many thanks for this gist nonetheless though!