Pretty much everything is optional if you stick to http/1.0. If you implement http/1.1 then you're required to do a lot of non-essential stuff like chunk encodi

Pretty much everything is optional if you stick to http/1.0. If you implement http/1.1 then you're required to do a lot of non-essential stuff like chunk encoding, pipelining, and provisionals which themselves are reasonably trivial too but they make the server code less elegant. If you want a protocol that's actually hard, implement SIP.