i am using Nios II 5.0 IDE and i try to create one project with the NIOS using the lwIP as Standalone. Is it possible to use the lwIP 0.7.1 without an operating system running with the NIOS II? I use the Linux as development platform and i tried to run the example "unixsim/simhost" from lwIP together with the NIOS but dont works. I thought the lwIP (api_lib.c) can provide the emulation of the operating system, but i dont understand why can I define the architecture (sys_arch.c, sys_arch.h) to my Hardware(NIOSII). I need really to do this? I am getting error "SYS_MBOX_NULL undefined" when i try to compile with the Nios IDE. Under Linux the unixsim run ok.