Typing /say @e on a server (only on a server) will disconnect all players from said server.
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Comments 6
Yeah, it's stupid for the admin to type /say @e. What are they thinking? I mean, if it crashes your server, you did it yourself. It's not like players can type /me @e to crash the clients in SMP. Oh wait. They can!
Basically, @e should have a max count. It could be limiting to commands, but considering the damage, at the very least listing commands should have a limit. You definitely wouldn't need as massive a list as is possible, and considering it is enough to disconnect clients, among other problems, it makes sense.
The server didn't crash; my friend was running it it and I asked him if it did. It didn't actually crash, but all the players were just randomly disconnected. Anyways, it wouldn't have been a large number, since we had adjusted gamerule doMobSpawning to false, and used /kill @e, neither of which put much stress on the server.
Try using a third party client to spam selectors on a 53GB world where each player needs 100MB of server memory because they're in a different corners of the map, and see if that server can hold up.
Doing that would attempt to list every single entity in existence (loaded chunks), which could easily be an absolutely ridiculous number. While you should not ever do that command as stated, the mistake of doing the command should not disconnect all players. There should be a limit in entity listing and action, similarly to how the new clone and fill commands have block/area limits, to prevent overloading.