Basics of Multiplayer with Steam

Introduction

I will try to explain the basics of multiplayer with Steam and the different ways to implement it. This guide is not a step-by-step tutorial, but rather an overview of the different concepts and methods.

Steamworks SDK

There are basically three ways/methods to use multiplayer with the Steam SDK. This may sound confusing at first, but it's actually quite simple. The three methods are:

Matchmaking and Lobbies

Let me quote from the Steamwork's website itself :

Steam's peer-to-peer matchmaking is built around the concept of a lobby. A lobby is a entity that lives on the Steam back-end servers that is a lot like a chat room. Users can create a new lobby; associate data with a lobby; search for lobbies based on that data; join lobbies; and share information with other users in the lobby. A single lobby can have up to 250 users in it, although typically most games have at most 2-16 players.

Now this is me speaking :

As you see, Lobbies are only existing on the Steam backend but but but, you can link a game server with a given lobby and it can be a Listen Server too.

P2P Networking

This is already built into the SteamSubsystem and whenever you travel to a new level, the SteamSubsystem will automatically create a new P2P connection. This will only happen if you have used the listen tag while travelling the level.

Game Servers

This is the most common and secure way to implement multiplayer. More info can be found here (opens in a new tab).

But don't worry if you don't want to read the whole Steamworks documentation, I will explain everything that matters under the Dedicated Servers section.