Currently, UE4 built-in networking is client-server. It would be cool for UE4 to support peer to peer networking in blueprints. The advantage of Peer to Peer networking is that that a server is not required. For a better performance, things could be instanced. For example, let's think of an online Hack n' Slash.
I too would like peer to peer it seems unreal removed it from Trello. For true P2P you can use current model but would need each player to run a client and server instance. Then brute force ip search for anyone with your game. I think you would need to create a virtual port on one of the common open ports to avoid legal issues.
Connecting Players via local network in ue4 through Hamachi(VPN). Client and server approach and why it is better than peer to peer approach. Replications and Server Authority (Server always right and has the authority to replicate other actors). Hosting Server with server Travel that makes the players travel from (Lobby to Game Map).
UE4's networking code isn't really designed around a P2P model, but a client-server model. For basic multiplayer code that's fine, though, you just have one of the clients also be the server. UE4's documentation calls this a "listen server" (as opposed to a "dedicated server", where the server is not also a player).
When it’s enabled for your game, you will have access to the following Steam features through UE4’s unified Online Subsystem API: • Online sessions and invites. • Matchmaking via peer-to-peer lobbies or dedicated servers • Firewall/NAT negotiation for peer-to-peer multiplayer via Steam Networking • Player authentication - new in 4.20
Using direct peer-to-peer connectivity may increase your game's upstream bandwidth usage. When transmitting a game or voice message through the cloud relay service, Party sends a single message to the service; the service then replicates and forwards the message to each target device. When transmitting a game or voice message through direct ...
Game Services deliver lobbies, matchmaking, peer-to-peer connectivity, player data storage, achievements and stats, leaderboards, game analytics, and player ticketing. More features are coming later, including voice chat. You can use these services together with your own account system, with platform account systems, or choose to use Epic Games ...
STUN and TURN Servers. In order for the Signaling and Web Server to be able to negotiate a direct connection between the Unreal Engine application and the browser, each party needs to send the other its own IP address. The browser needs to be able to access the IP address sent by the UE4 application, and vice-versa.
UE4 does not have P2P built in. If you go look at their trello it is in the wish list part of networking :(. But UE4 has an online subsystem thing where you can plug in steamworks and use that for P2P.