I've forgotten the details, but tftpd-hpa is "quirky". I did figure it out once, but nowadays I generally just avoid it and install the traditional tftpd server instead.

As for xinetd, that thing is also a bloody nuisance. I suggest you initially just avoid it completely, and run a standalone tftpd server. Once you get *that* working, then think about converting it to use the xinetd superserver. But only then.

Cheers