Parsing can be "fun", trying to figure out if text is ended with \n, \r, or both.

Unix's \n, Windows' \r\n, and older Mac's \n\r.

Deciding whether a line-end terminated when reading from a network is kinda hard...

older macs are just \r not \n\r

\r?\n regex?

No, you want \R, the generic Unicode linebreak sequence.

http://pcre.org/current/doc/html/pcre2pattern.html#newlinese...

http://p3rl.org/rebackslash#\R

So, you take a `\r` from the network. So, do you wait for a `\n` before returning the line?

You wait to peek the next byte, or EOF, and then make the choice.

Line protocols do not transmit EOF (and the problem is on each line anyway). And the next byte may only come after you write something on the socket.