Communication & Coordination

Origins

Team messaging in classic Robocode grew out of the RoboWiki community's TeamRobot examples and discussion. Robocode Tank Royale, created by Flemming Nørnberg Larsen (fnl), ships a structured message API with its own per-turn and per-message limits.

Team Basics teaches a bot not to shoot a teammate. That stops the obvious disaster, but two bots that merely avoid each other's bullets are still just two duelists who happen to share a battlefield. Coordination needs an actual design: what to send, how often to send it, and what a teammate does the moment it arrives.

A budget before a protocol

Classic Robocode's TeamRobot has two ways to send a Serializable message: broadcastMessage(message) reaches every teammate, and sendMessage(name, message) addresses one teammate by name. Tank Royale offers the same two choices with broadcastTeamMessage(message) and sendTeamMessage(teammateId, message).

Classic Robocode caps each message at 32,768 bytes after Java serialization. Tank Royale limits each bot to 64 packets per turn, with at most 128 logical payloads across ordinary packets and batches. Each packet may use 49,152 UTF-8 bytes, and the compact packet array may use 262,144 UTF-8 bytes. A batch keeps ordered entries in one packet and one event, which helps when several updates must arrive together.

Give every message a shape

A message that is just a raw number or a bare string works fine until two bots disagree about what it means. Tank Royale's own documentation settles on a plain type-tagged format that keeps that disagreement from happening:

• ENEMY|Tracker|x:250,y:300,h:45,e:80,t:150 for a spotted enemy's position, heading, energy, and scan time
• TARGET|Tracker|MyBot for which enemy a bot has claimed
• STATUS|MyBot|x:100,y:100,e:100 for a routine check-in
• HELP|MyBot|x:100,y:100,e:20 for a bot in real trouble

Every teammate reads the type tag first and only parses the fields that type promises, so adding a new message type later never breaks an older one. Sending this shape on every tick still burns through the 10-message budget in three turns, so the discipline is to send on a real change, a newly scanned enemy, a claimed target, a status swing, not on a clock.

Claim a target instead of guessing

Left alone, two bots on a team both default to the same instinct: shoot whatever is closest. Twin Duel Strategy Guide already shows the cost of that instinct when both bots pick the same enemy and leave the other untouched. A TARGET message fixes it before a shot is even fired:

for enemy in scannedEnemies:
    if not claimedByTeammate(enemy):
        myTarget = enemy
        broadcast("TARGET|" + myName + "|" + myTarget)
        break

Each bot checks incoming claims before picking its own, so the team spreads its fire across the enemies present instead of stacking two guns on one and leaving another free to aim back unopposed.

A friendly bot claims a target by message, so its teammate holds fire instead of doubling up.

Ask for help before the fight is already lost

A HELP message earns its keep exactly once: the moment a bot's energy crosses into real danger. The Tank Royale example fires it at energy 20, reporting position and energy in the same breath so a teammate can decide whether to peel off and cover, or let a low-energy bot's ramming sacrifice do the job instead. Firing it earlier just spends the message budget on noise, and firing it too late spends it on an obituary.

Platform notes

Platform Difference

Both platforms support broadcast and directed messages. Classic Robocode limits each Java-serialized message to 32,768 bytes. Tank Royale also limits per-turn traffic to 64 packets and 128 logical payloads, plus 49,152 UTF-8 bytes per packet and 262,144 UTF-8 bytes for the compact packet array. A failed Tank Royale intent is rejected in full, and accepted messages arrive on the next turn.

Further Reading

• Teams - RoboWiki (classic Robocode)
• Team Messages - Tank Royale documentation
• Team Strategies - Tank Royale documentation