this has been fine working since the 80s

  pc1> tar c <SRC_FOLDER_OR_FILES> | nc -l 12345

  pc2> nc <IP_OF_PC_1> 12345 | tar xv -C <DST_LOCATION>

No auth? I like to live dangerously too lol.

Jokes aside, the probability of it being exploited is low though.

Also, this assumes pc1 has a publicly, where as with Croc and MW, you can transfer files between two PCs on both behind different NATs.