How to test UDP port connectivity

I had to configure a new service which listened on a UDP port and would accept data. This was setup but my question was how to actually test the connectivity of the port and ensure data was acceepted.

To do this I wrote a python script:

import socket

server_address = ('your_server', UDP PORT)  # Replace 'your_server' with the actual server IP address/hostname
# Replace UDP PORT with the actual UDP port number

client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
message = b"Hello, server!"  # Your message goes here

try:
    client_socket.sendto(message, server_address)
    print("Message .")
except Exception as e:
    print(f"Error sending message: {e}")
finally:
    client_socket.close()

Now on the remote machine you can run:

sudo tcpdump -i <interface> udp port <UDP PORT>

Ensure tcpdump is installed. Replace <interface> with the actual interface name, e.g. eth0 and <UDP PORT> with the actual UDP port number. Find the interface with ifconfig or similar

Run tcpdump and then run the python script, you should see the message appear in the tcpdump output.