Unity Multiplayer is the easiest way to create real-time, networked games for Unity. It’s fast to implement and highly customizable. Unity-provided servers ensure that your players can find and play with each other.
Note: If you are upgrading your multiplayer project from an earlier version of Unity (before 5.4), there a number of changes to the API which you may need to update in your project. For more information, see the 5.4 networking upgrade guide.
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.