Test your board with the following code:

#!/bin/bash

IP=192.168.123.456

while true
do 
  sleep 0.04
  dd if=/dev/urandom bs=1200 count=1|nc -u $IP 60001         
  echo -n 'La'|nc -u $IP 60000
done

All the available channels should now blink with pretty colors !

If you have several boards, send the data to each board in turn then broadcast the 'La' sync packet to the x.x.x.255 address so they all receive the signal at the same time.

You can check the order of the strips and verify the pixel mapping with this slightly more elaborate script :

#!/bin/bash

[ "$IP" ] || IP=192.168.41.104

while true
do

  WHITE=$(printf "\377\377\377")
  HEAD=""

  for i in $(seq 0 399)
  do
    sleep 0.1
    HEAD=$HEAD$WHITE
    echo -n $HEAD|nc -u $IP 60001
    echo -n 'La'|nc -u $IP 60000
  done

done

Note that the physical and logical order of the inputs are reversed. It's a litlle idiosynchrasy of the variable-output logic, it must be reversed in software but it makes the hardware faster and smaller.