How to detect if network is dropping UDP packets?

at server side, establish a UPD server with

iperf -s -u

at client side, check UDP connection with

iperf -u -c <IP Address of Server>

You can try to establish a UDP connection with netcat.

On a machine A outside the consumer's network run:

nc -u -l -p 1234            # if using netcat-traditional
nc -u -l 1234               # if using netcat-openbsd (as pointed out by @JamesHaigh)

Note the -u which instructs netcat to use UDP. (And also be aware, that there are different versions of netcat, which will need the -p parameter or not; given are the variants for the two most common(?) ones, both included in Debian.)

On consumer location: nc -u [addr of machine A] 1234.

Try to send send some text, or even better use pipes to send a file between both locations and do a diff afterwards.