4 players, 2 teams, automatic serve rotation.
Serve then follows the standard doubles order: the receiver becomes the next server, serving to the first server's partner, then that player's partner, and back to the start. Every 2 points, or every point from 10-10.
Free on-court doubles scoreboard from Pong Home. Enter 4 player names, pick the first server and receiver, and the app tracks scores, games, and the doubles serve rotation automatically, showing which team is serving and to which player.