Try Packet Sender (available for all major OS: I used the portable version for Windows as well as the AppImage for Linux (I love that AppImage-idea. Already the third OSS which was packaged like this instead of a *.deb or as pure source ..)) to emulate the sending of some UDP-datagrams to test one of my programs. And it works really neatly.
You’ve got a tidy window with some textfields for receiver, type and content, a “fire away”-button, some repeat-ability. Nice!
On the receiving end we all know Wireshark. But the emulation was (at least to me) before some big black hole.
Yes, I know, there would be as well sendip. But at work I barely could make a Cygwin work. Not to speak about some dynamic “oh, I load more packages on the fly from the internet”-possibility, meh.
But for those interested: short tutorial for sendip.