Details: when you click on Enable UDP trigger in the preferences it will start listening on the UDP port configured. (You still need to "arm" the trigger as for audio in the capture screen (lightning icon)).
The UDP message itself is ignored, you can send an empty string.
It works from different computers. I just double checked by installing an app called "UDP Sender / Receiver" on my mobile phone and I was able to trigger the capture remotely. (In this case it insisted on sending a message so I just set it to "a").
Here is a small python script sending a packet every 10 seconds. You can send to the IP of the computer with Kinovea. If you don't know it you can send to 255.255.255.255.
import os
import socket
import time
# Send an empty udp broadcast every 10 seconds.
def broadcast():
print(f'Broadcasting at {time.ctime()}')
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
s.sendto(b'', ('192.168.0.228', 8875))
s.close()
if __name__ == '__main__':
while True:
broadcast()
time.sleep(10)