Tongyu Zhou, March 2022
Fish-Networking, or Fishnet, is a very new (released 2/24/22) networking solution for Unity created by First Gear Games, a game design company that has been making tutorials and extensions to Mirror for a long time. Fishnet is server-authoritative by design, but does allow users to act as both server and client for rapid testing. Their transport system supports any kind of network topology. While new, the initial comments on the Unity Asset Store from users who are familiar with other networking solutions such as Mirror, Photon/PUN, and Unity's built in system have praised it as easier to use and faster than its predecessors. Another major benefit is that Fishnet was built from the ground up and thus has a very clean code base.
Since this plugin is very new, the size of the community is significantly less in comparison to those of more established plugins. However, their Discord is very active and the developers answer questions on there fairly quickly. They also have an active Trello board so that users can see new features that will be implemented, as well as their own tutorial series on Youtube.
The documentation for Fishnet can be found here and its API here. Currently, it supports Unity 2019LTS, 2020LTS, and 2021. In addition to guides informing the user on how to migrate to Fishnet from existing frameworks, it also provides a direct comparison with Mirror, summarized as follows:
Moving object bandwidth:
Performance when scaled:
Synchronize more data types
SyncVar, SyncObject, RPCs
Better customization for features
Clear and completely commented API and XML
Built-in client-side prediction
Fast domain reload support
Powerful single, additive, stacked scene management
Advanced interest/observer system
Supports WebGL, Steam