Question How does UNET Multiplayer HLAPI relate to the new game services multiplayer?

Hi RR7,

First, to answer your questions directly:

• The new Relay service does not use the same backend as the UNet service
• The UNet Relay service is past its critical support and may shut off at any time
• HLAPI is not compatible with the new Unity Transport Protocol (UTP)

With UNet services approaching depreciation, we've received a lot of similar questions about UNet. So, I wanted to take the opportunity to talk about some of the histories of Unity's networking solutions and give some context about how things evolved and the relationship between them. I had to do a bit of digging, so if there are any mistakes or anything is unclear ill edit as necessary:

On May 12th, 2014, Unity announced the launch of a new networking solution known as UNet, which consisted of two major components: the High-Level API (HLAPI) and Low-Level API (LLAPI, sometimes referred to as the "transport layer." HLAPI can be thought of as the "engine integration" responsible for translating data into a format that could be easily transmitted across a network and managing the transmission of that data. HLAPI was built on top of LLAPI, which was responsible for directly handling connections such as establishment, flow control, statistics, and network discovery. Around this time, Unity also released a few services built on top of UNet, namely P2P Relay and Matchmaker.

On January 5th, 2018, a new third-party project called MLAPI (Mid-Level API) was announced on the forums. This package was an alternative to the HLAPI by including more features with better performance. That same year MLAPI Relay was published along with a compatible fork of the HLAPI. It should be noted that at this point, these packages were not created nor supported by Unity but were rather third-party community contributions.

After creating UNet and maintaining it for six years, we collectively learned a ton about what creators need in a networking solution. Mixing that with the list of feature requests and the success of alternative frameworks, it became apparent that we needed to rearchitect a better solution. Therefore, on August 2nd, 2018, a blog post was published announcing the depreciation of HLAPI, LLAPI, Relay, and Matchmaker while we worked on a replacement. Around the same time, their creators made the source code for the MLAPI services open source.

On December 3rd, 2020, MLAPI officially joined Unity along with its creator. Our blog post talked about how we would be evolving MLAPI to work better with the existing work done developing the new networking solution, primarily concerning integrating it with our new replacement for the LLAPI known as the Unity Transport Protocol, or UTP. With the help of the MLAPIs creator, this was completed in relatively short order, and four months later, we were able to launch an experimental version of MLAPI + UTP.

In the summer of 2021, MLAPI was officially renamed "Netcode for GameObjects" (aka "Netcode" or "NGO"). With the 1.0.0 release of NGO, we also published guides for migration of:

• MLAPI 0.1.0 to NGO 1.0.0
• MLAPI <12.1.7 to NGO 1.0.0
• UNet to NGO 1.0.0

In October 2021, we released the beta version of Unity Game Services, or UGS, including many managed services such as the new Relay service. These services use completely new infrastructure, including different servers and APIs, and are entirely separate from the depreciated services. While these services are intended to be modular, official support is only offered for the new networking packages.

According to the published depreciation schedule, HLAPI would receive only critical support until early 2021, while LLAPI, legacy Relay, and legacy Matchmaker would receive critical support until early 2022. As of this writing, all products and services are considered depreciated. While they may retain functionality for some time, we will no longer update the packages and may shut the servers off permanently at any time.

MLAPI represents an entirely different approach to networking. There is no way to adapt code from HLAPI to MLAPI and by proxy from HLAPI to NGO without rewriting the networking logic. HLAPI is considered completely incompatible with UTP, and while it may be possible to use LLAPI with Netcode, there will likely be some significant challenges.

 

We are going to close this forum thread out, but please feel free to make a new post if you have any follow up questions. Thanks for your time!