First of all, I want to express my gratitude for the excellent work you've done, providing such valuable resources for everyone to learn from.
I encountered the error shown in the screenshot while compiling INET.

Based on the error info in the screenshot, I found that the variable 'randDst' declaration can't be found in both UdpPfrpApp.cc and UdpPfrpApp.h.
After adding declaration of the variable 'randDst' in file UdpPfrpApp.h, I was able to compile successfully.
I hope this issue can be resolved in this project.