[MC-34749] Hopper: java.lang.IllegalStateException: failed to create a child event loop

Moderator Note

This issue is most commonly caused by a broken installation of Avast! free edition Anti-virus software. A reinstallation of Avast! and a reboot usually fixes it.
- McAfee anti-virus software (and derivatives) are also know to cause this issue, and currently the only known solution is to uninstall this software to correct the problem.
- Also Outpost security may cause that issue.
This error also occurs when Java tries to open a socket on the IPv6 stack, but could't get a connection to the outside world. Try forcing the use of the IPv4 stack by adding -Djava.net.preferIPv4Stack=true to the JVM Arguments in your launch installation (to edit your JVM arguments, click "Edit" on the profile you are using, then click "More Options").

Please visit Community Support for further support.

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-294053/

Crash:

java.lang.IllegalStateException: failed to create a child event loop
	at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:61)
	at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:49)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:61)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:52)
	at mo.<init>(SourceFile:36)
	at net.minecraft.server.MinecraftServer.<init>(SourceFile:114)
	at brh.<init>(SourceFile:38)
	at ays.a(SourceFile:1585)
	at bbs.e(SourceFile:162)
	at bbt.a(SourceFile:214)
	at bam.a(SourceFile:186)
	at bbs.a(SourceFile:187)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// Don't do that.

Time: 10.10.13 17:10
Description: Rendering screen

java.lang.IllegalStateException: failed to create a child event loop
	at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:61)
	at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:49)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:61)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:52)
	at mo.<init>(SourceFile:36)
	at net.minecraft.server.MinecraftServer.<init>(SourceFile:114)
	at brh.<init>(SourceFile:38)
	at ays.a(SourceFile:1585)
	at bbs.e(SourceFile:162)
	at bbt.a(SourceFile:214)
	at bam.a(SourceFile:186)
	at bbs.a(SourceFile:187)
	at bkv.b(SourceFile:851)
	at ays.ab(SourceFile:783)
	at ays.e(SourceFile:706)
	at net.minecraft.client.main.Main.main(SourceFile:103)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
	at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:128)
	at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:120)
	at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:87)
	at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:57)
	... 15 more
Caused by: java.io.IOException: Unable to establish loopback connection
	at sun.nio.ch.PipeImpl$Initializer.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.nio.ch.PipeImpl.<init>(Unknown Source)
	at sun.nio.ch.SelectorProviderImpl.openPipe(Unknown Source)
	at java.nio.channels.Pipe.open(Unknown Source)
	at sun.nio.ch.WindowsSelectorImpl.<init>(Unknown Source)
	at sun.nio.ch.WindowsSelectorProvider.openSelector(Unknown Source)
	at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:126)
	... 18 more
Caused by: java.net.ConnectException: Connection refused: connect
	at sun.nio.ch.Net.connect(Native Method)
	at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
	at java.nio.channels.SocketChannel.open(Unknown Source)
	... 26 more


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:61)
	at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:49)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:61)
	at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:52)
	at mo.<init>(SourceFile:36)
	at net.minecraft.server.MinecraftServer.<init>(SourceFile:114)
	at brh.<init>(SourceFile:38)
	at ays.a(SourceFile:1585)
	at bbs.e(SourceFile:162)
	at bbt.a(SourceFile:214)
	at bam.a(SourceFile:186)
	at bbs.a(SourceFile:187)

-- Screen render details --
Details:
	Screen name: bry
	Mouse location: Scaled: (203, 62). Absolute: (406, 355)
	Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2
Stacktrace:
	at bkv.b(SourceFile:851)
	at ays.ab(SourceFile:783)
	at ays.e(SourceFile:706)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w41a
	Operating System: Windows Vista (amd64) version 6.1
	Java Version: 1.6.0_13, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
	Memory: 132615600 bytes (126 MB) / 170655744 bytes (162 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w41a
	LWJGL: 2.9.0
	OpenGL: GeForce GT 220/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: [faithful32pack.zip]
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: ~~ERROR~~ NullPointerException: null

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-294053/16540251/

Hopper: java.lang.IllegalStateException: failed to create a child event loop - Caused by AntiVirus / Firewall software