There is a proof-of-concept branch (season2) where I was experimenting with features such as LAN and netplay. The branch is outdated, because we are in the middle of a big refactor related to this, but regardless it is promising.

LAN was fairly close to a finished product. There were still issues to iron out but it seemed to work fairly well over a reliable (ie. ethernet) network. Wifi is another affair.

Netplay was a clunky proof of concept at best. It worked somewhat, but was very rough and unfinished. Netplay will also benefit the most from our refactor -- it would greatly simplify the process.

These features should entirely negate the need for things like Hamachi, while providing far more reliable multiplayer support than the old UDP-based system ever did.

As Generic said, the old system was basically just tossing packets over the network with zero guarantee. In the best case scenario it happened to work, but as it made no attempt at synchronizing the various players, it was doomed to fail. Local multiplayer in the old days was finicky, required workarounds like disabling the framerate limiter, and was overall not very good -- several games just refused to connect entirely, and those that did tended to lag a lot. By comparison, local multiplayer in 0.9.5 is smooth as butter -- improvements to wifi emulation, but there's also a whole synchronization system in place to keep all the players running at the same pace, so no data gets lost.

Also, an important fact regarding local multiplayer comm is that the protocol relies on low latency. When the host sends a data frame, clients are given a specific time window (expressed in microseconds) where they need to respond. The replies may not be late, they either arrive on time or they don't -- that is how it works in the real world. Emulating this is already quite complex, and if you have to deal with added network lag (often measured in hundreds or thousands of microseconds), it doesn't bode well.

Around the 0.9.5 release, we experimented with multiplayer over LAN by backporting the old UDP comm layer. With a fast enough network, it mostly works. However, the new comm layer introduced in 0.9.5 add several checks and smarts to make sure the aggressive synchronization only kicks in when needed and doesn't cause lag spikes. I had to work around the weirdness that some games exhibit.

The LAN feature in the season2 branch was a renewed attempt at this sort of thing, but using enet instead of raw UDP comm, and trying to replicate the checks and smarts of the shared-memory based system, with moderate success.


Regarding season2: the builds were deleted because apparently there is an expiration time to CI builds.

If you're running Windows, Nadia provided a build: https://kuribo64.net/get.php?id=QCFE5vdbQtwNtqWP

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