All of this is thanks to the effort put together by the GBA homebrew devs, being lead by the GameBoy Development community over at gbdev.io, where they share a vast variety of libraries and documentation about the GameBoy family of handhelds, put together over the decades to allow for homebrew developers and romhackers alike to create new and fascinating projects for the beloved Nintendo handheld.
One such collection of libraries is the GBA Link Connection, which allows for the developer to interact with the serial port found in the Game Boy family of systems, which was frequently used to allow some sort of multi-player functionality with the handheld when connected to other Game Boys. The goal of GBA Link Connection is to allow homebrew games to make full use of the serial port, and allow multi-player functionality within homebrew developed games.
During the weekend, the GBDev team showcased a breakthrough for these libraries, that one being the Link Cable Multiboot library and Link Wireless Multiboot library, which allow for a Game Boy Advance game with either the Link Cable or the Wireless Adapter connected to send over small 256KiB programs to other GBA systems.
This opens up a lot of possibilities for homebrew development for the Game Boy, Game Boy Color and Game Boy Advance systems, as this could possibly be compared to some degree to what the DS did for some multiplayer games when it came to connections with other DS systems that didn't have the same cart inserted.
Those interested can check out the GBA Link Connection set of libraries over at their open source GitHub repository.
GBA Link Connection Library at GitHub
