Any p2p port with good netcode?

Choco doesn't have P2P netcode.

For your purposes Chocolate Doom is "peer to peer". However, I find that the terms "client-server" and "peer to peer" are misleading and don't really capture the distinction between the networking code in say, Quake and Doom.

Not sure exactly what you want.

See DoomLegacy docs:
http://doomlegacy.sourceforge.net/docs/legacy.html

A network game can be started either using the commandline parameters -server and -connect, or from the multiplayer menu that allows you to connect to a server or create one yourself.

Auto-detect a server on a LAN.
$ doomlegacy -connect

This only works when computers are directly connected. If you play through internet, the server can NOT be auto-detected, and you must specify it's IP address.

Example A, 3 players on a LAN:
player 1 (the server)
$ doomlegacy -server 3
player 2 (client)
$ doomlegacy -connect
player 3 (client)
$ doomlegacy -connect

Example B, 2 players, through internet:
player 1 (the server)
$ doomlegacy -server 2
player 2 (client)
$ doomlegacy -connect xxx.xxx.xxx.xxx

Example C, a 3 player game, with _TWO_ computers, one is split-screen:
player 1 (the server)
$ doomlegacy -server 3
player 2 and 3 (2 clients on the same computer)
$ doomlegacy -splitscreen -connect

XCOPY said:

Chocolate-doom should be one to consider, just waiting for a new version to come up with fixed sound in multiplayer.

Use the latest build from here:
http://www-users.cselabs.umn.edu/~delbe001/chocolate-doom/
The sound is now fixed.