The sixth generation (6G) of wireless technology is seen as one of the enablers of real-time fusion of the physical and digital realms, as in the Metaverse, extended reality (XR), or Digital Twin (DT). This would allow people to interact, work, and entertain themselves in immersive online 3D virtual environments. From the viewpoint of communication and networking, this will represent an evolution of the game networking technology, designed to interconnect massive users in real-time online gaming environments. This article presents the basic principles of game networking and discusses their evolution towards meeting the requirements of the Metaverse and similar applications. Several open research challenges are provided, along with possible solutions.