Video widget does not work when using netcat


I’m trying to make the video widget working, but without success.

I have a raspberrypi on a drone that takes a video and redirect it to the phone by a router. here is the command in the router

sudo ./rx -b 8 -r 4 -f 1024 wlan1 | netcat -u 5700

rx is a program that receives the video from the network and netcat redirects it to the phone ip address

here is the command on the drone
raspivid -ih -t 0 -w 1024 -h 720 -vf -fps 24 -n -g 64 -pf high -o - | ./tx -p 0 -b 8 -r 4 -f 1024 wlan1"

tx is a program that sends to the wifi interface wlan1 the video stream

The no video data disappears but I still get a black screen.
The video format is the following (taken with a raspberry pi) 1024x720 24fps h264 encoding

the tower app version is 3.2.1.beta1 and the video widget configuration is “custom video stream udp port 5700”

what’s wrong with my config ?

thanks in advance