Unity Relay
Unity Relay exposes a way for game developers to securely offer increased connectivity between players by using a join code style workflow without needing to invest in a third-party solution, maintain dedicated game servers (DGS), or worry about the network complexities of a peer-to-peer game. Instead of using DGS, the Relay service provides connectivity through a universal Relay server acting as a proxy.
The Relay service has two key components: the Relay servers and the Relay Allocations service.
Tip: Checkout How to setup Global Matchmaking for Unity by Tarodev.