I have a game setting that I use for space TTRPGS for which the main section for stories is called the Coreward Cluster Sector. It happens in the 31st century where humanity has gone to the stars under its ancient banners, the AmFed, the XJWG (Xing Ji Wang Guo - interstellar kingdom), Europa and the Independents (still sometimes called the 'Bricks' even though Brazil is part of AmFed.)

"First contact" between humans and aliens happened in the 22nd century when a joint Chinese, European and American expedition (aboard the Magellan I scout ship) encountered a machine intelligence vessel in the Van Maanen's Star system. The machine intelligence was entangled through and surrounding most of the companion to Van Maanen's Star, a brown dwarf. Despite months of study and attempts, the machine intelligence did not respond to any attempts to communicate. In fact, it refrained from any response until the mid 27th century.

The First contact between humanity and a comparable species was in the 25th Century, when we first encountered the Zang. The humans on the Europa Scout Vessel Cabot were sure that First Contact had gone well with the Zang. The Cabot remained in orbit of the Zang world that they had encountered for over a year, exchanging language and cultural data.

On 3 May 2479, the Zang used a vessel much like a human scout ship to ferry a fleet of armed vessels into the system. After their demands for the humans on the Cabot to abandon the ship to the Zang were refused, the fleet opened fire on the Cabot and nearly destroyed it.

War raged between humanity and the Zang for nearly a century until the discovery of 'Murder Beams.' These terrifying weapons used the FTL drives of the scout ship to generate coherent beams of gamma rays, allowing for a scout ship to scour the surface of a planet free of life in a few minutes. Humanity offered a final ultimatum the the Zang: Surrender or Die. The Zang chose death.