Not receiving UDP message on local machine

Question

So I have two machines, a laptop and a raspberry pi 4. I am trying to send UDP packets to the pi from my laptop.

C# code running on laptop:

            public static void SendMessage(string msg, IPEndPoint endPoint)
            {
                using (UdpClient client = new())
                {
                    var message = Encoding.ASCII.GetBytes(msg);
                    client.Send(message, message.Length, endPoint);
                }
            }

which I am calling in Main():

        static void Main(string[] args)
        {
            new Thread(()=>
            {
                while (true)
                {
                    for (int i = 0; i < 256; i++)
                        Networking.UDP.SendMessage("Hello World!", new IPEndPoint(IPAddress.Parse($"192.168.1.{i}"), 11000));
                    Console.WriteLine("Message sent");
                    Thread.Sleep(1000);
                }
            }).Start();
        }

On the raspberry pi I am running this simple python script:

import socket

hostname = socket.gethostname()

local_ip = socket.gethostbyname(hostname)
local_port = 11000

UDPsocket = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
UDPsocket.bind((local_ip, local_port))

print("Now listening on port "+str(local_port))

while (True):
    bytesAddressPair = UDPsocket.recvfrom(1024)
    message = bytesAddressPair[0]
    address = bytesAddressPair[1]
    print(str(address)+" : "+str(message))

However, the raspberry pi program does not seem to receive any messages. What am I doing wrong?

Answer 1

(Edit: First comment on this answer explains the reason)

Figured it out. On the pi, in order to get the local IP I was using

socket.gethostbyname(socket.gethostname())

which apparently was not the correct way to get the local IP. Someone might be able to further explain why that was not producing the correct outcome. To solve the issue I just ran hostname -I on the pi to find the correct local IP and used that in the code, with the final receiving code being:

import socket

local_ip = "192.168.1.10" #Your local IP here obtained from terminal
local_port = 11000

UDPsocket = socket.socket(family=socket.AF_INET, type=socket.SOCK_DGRAM)
UDPsocket.bind((local_ip, local_port))

print("Now listening on port "+str(local_port))

while (True):
    bytesAddressPair = UDPsocket.recvfrom(1024)

    message = bytesAddressPair[0]

    address = bytesAddressPair[1]

    print(str(address)+" : "+str(message))