You can try "/say @e" in the game or the console.
ALL THE PLAYERS will be kicked
They can join the game again..But a few minutes later the server will crash with OOM.
MC-132465
"/say @e" kicks everyone out of server
Resolved
Duplicate
0
Duplicate of MC-45838. About the OOM however, I have never seen that as a side effect of that bug. You'll have to make a new bug report and include the crash log.