Thank you Simon for the prompt response.
I have not reason for calling lwip_init() instead of tcpip_init(). I'm just trying to understand what pieces are required to simply send a UDP packet. After looking at a few other examples, and the FreeRTOS example for the AVR32, what I'm trying to do makes sense if I were to run bare metal. Which is what I see in a bunch of other examples like the omapl138 (Sitara).
Your respond confirms what I've seen in other OS examples (not bare metal) of the lwip port and I will cease from going down that path. So even for a udp sender sounds like I still need to call the tcpip_thread.
Thanks