If you are using bash, you might as well write
echo -n "hello" >/dev/udp/localhost/8000
and avoid all the idiosyncrasies and incompatibilities of netcat.
This also works sending to other hosts, ex:
echo -n "hello" >/dev/udp/remotehost/8000
These are not “real” devices on the file system, but bash “special” aliases. There is additional information in the Bash Manual.