[MC-230525] Dedicated server failing to bind to port causes NullPointerException

The bug

When the dedicated server fails to bind to the specified port, e.g. because another application is already using that port, a NullPointerException occurs:

1.17.1-pre1

[15:59:42] [Server thread/WARN]: **** FAILED TO BIND TO PORT!
[15:59:42] [Server thread/WARN]: The exception was: java.net.BindException: Address already in use: bind
[15:59:42] [Server thread/WARN]: Perhaps a server is already running on that port?
[15:59:42] [Server thread/INFO]: Stopping server
[15:59:42] [Server thread/INFO]: Saving worlds
[15:59:42] [Server thread/ERROR]: Exception stopping the server
java.lang.NullPointerException: Cannot invoke "abr.o_()" because "Γÿâ" is null
        at net.minecraft.server.MinecraftServer.a(SourceFile:592) ~[1.17.1-pre1.jar:?]
        at net.minecraft.server.MinecraftServer.u(SourceFile:619) ~[1.17.1-pre1.jar:?]
        at aas.u(SourceFile:585) ~[1.17.1-pre1.jar:?]
        at net.minecraft.server.MinecraftServer.x(SourceFile:729) ~[1.17.1-pre1.jar:?]
        at net.minecraft.server.MinecraftServer.a(SourceFile:274) ~[1.17.1-pre1.jar:?]
        at java.lang.Thread.run(Thread.java:831) [?:?]

Expected would be that the server cleanly exits without any exception.

Reproduction steps

Download the dedicated server from https://www.minecraft.net/en-us/download/server
Start the server twice on the same port (you might have to start them in separate folders)
❌ The second server shows a NullPointerException in the log

Linked issues

is duplicated by 4

MC-143246 Exception when shutting down server if port already in use Resolved

MC-228310 Server Bug Resolved

MC-230179 Error on start up for a server (Cannot invoke "abr.o_()" because "Γÿâ" is null") Resolved

MC-236265 Minecraft Server gives java errors, doesn't start Resolved

relates to 1

MC-227537 Crash: java.lang.NullPointerException: Cannot invoke "it.unimi.dsi.fastutil.objects.ObjectSet.remove(Object)" because "$$4" is null Resolved

Comments 1

Einfxch_Finn 2023-03-20T17:04:06Z

Can confirm in 1.19.4

The server now throws an IllegalStateException before the NullPointerException

[17:54:28] [Server thread/WARN]: **** FAILED TO BIND TO PORT!
[17:54:28] [Server thread/WARN]: The exception was: io.netty.channel.unix.Errors$NativeIoException: bind(..) failed: Address already in use
[17:54:28] [Server thread/WARN]: Perhaps a server is already running on that port?
[17:54:28] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.IllegalStateException: Failed to initialize server
        at net.minecraft.server.MinecraftServer.runServer(SourceFile:688) ~[server-1.19.4.jar:?]
        at net.minecraft.server.MinecraftServer.lambda$spin$2(SourceFile:266) ~[server-1.19.4.jar:?]
        at java.lang.Thread.run(Thread.java:833) ~[?:?]
[17:54:28] [Server thread/ERROR]: This crash report has been saved to: /home/finn/vanilla/./crash-reports/crash-2023-03-20_17.54.28-server.txt
[17:54:28] [Server thread/INFO]: Stopping server
[17:54:28] [Server thread/INFO]: Saving worlds
[17:54:28] [Server thread/ERROR]: Exception stopping the server
java.lang.NullPointerException: Cannot invoke "net.minecraft.server.level.ServerLevel.getWorldBorder()" because "$$5" is null
        at net.minecraft.server.MinecraftServer.saveAllChunks(SourceFile:545) ~[server-1.19.4.jar:?]
        at net.minecraft.server.MinecraftServer.stopServer(SourceFile:606) ~[server-1.19.4.jar:?]
        at net.minecraft.server.dedicated.DedicatedServer.stopServer(SourceFile:536) ~[server-1.19.4.jar:?]
        at net.minecraft.server.MinecraftServer.runServer(SourceFile:707) ~[server-1.19.4.jar:?]
        at net.minecraft.server.MinecraftServer.lambda$spin$2(SourceFile:266) ~[server-1.19.4.jar:?]
        at java.lang.Thread.run(Thread.java:833) ~[?:?]