Question. Does this run in Linux on arm? Or does it run on the CPU (be it hardware or emulated)?
Bonus question: How can I answer that question for myself in the future when looking at similar source? Said differently: What am I looking at here? :)
It runs on an OS (POSIX compliant). If you look at connect.s you can see that he uses syscalls (connect()/socket()).
It's roughly what would produce a simple compiler targeting linux.
Otherwise, it would have had to write a TCP stack, drivers, ...
He uses Linux sys calls, which means the kernel needs to be there (and a libc of some sorts)... but that's all that's needed. So, with the RPi, you could essentially "boot" this code with pretty much a bare-metal system otherwise.
Bonus question: How can I answer that question for myself in the future when looking at similar source? Said differently: What am I looking at here? :)