Well Altera the equivalent is Signaltap, which you can use.
But given you are doing the encapsulation of the ADC data in HDL code and not the Nios-II, means that the problem is probably on the receive side of the connection (the PC), that's assuming you've simulated your HDL code and know it only produces the correct UDP packets for all settings especially those that are jumbo frames i.e. greater than the 1500 bytes of payload. Or maybe that is your problem you are producing bad packets that aren't jumbo frames?
Have you tried a different PC with wireshark? Perhaps the PC you are using has a virus or something on it. From what I've read it appears that the DCERPC protocol is a target for exploits, it's had a number of issues on windows platforms.