Failed to create a child event loop - intellij-idea

Question

In IntelliJ IDEA Community Edition 14.0.2, I'm trying to run Java Applet and every time I try to run project, I got this this dummy error.
Error: Failed to create a child event loop
What I've tried
Compiling newly created Hello World program
Update IntelliJ
Uninstall & Reinstall
Allow from Windows Firewall rule
Disabling Antivirus Program
I'm using Windows 8.1 with Anti-virus program Windows Defender.
Error detail from Log file:
java.lang.IllegalStateException: failed to create a child event loop
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:81)
at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:50)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:72)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:58)
at org.jetbrains.io.BuiltInServer.start(BuiltInServer.java:60)
at org.jetbrains.ide.BuiltInServerManagerImpl$1.run(BuiltInServerManagerImpl.java:111)
at com.intellij.openapi.application.impl.ApplicationImpl$8.run(ApplicationImpl.java:405)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
at org.jetbrains.ide.PooledThreadExecutor$1$1.run(PooledThreadExecutor.java:56)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:127)
at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:119)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:97)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:31)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:77)
... 12 more
Caused by: java.io.IOException: Unable to establish loopback connection
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:101)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:68)
at java.security.AccessController.doPrivileged(Native Method)
at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:170)
at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50)
at java.nio.channels.Pipe.open(Pipe.java:155)
at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127)
at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44)
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:125)
... 16 more
Caused by: java.net.SocketException: Network is unreachable: connect
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:457)
at sun.nio.ch.Net.connect(Net.java:449)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:647)
at java.nio.channels.SocketChannel.open(SocketChannel.java:189)
at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:130)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
... 24 more

Answer 1

Restarting intelliJ did not help, restarting machine did!

Answer 2

Disable firewall
or add idea.exe full correct path to outgoing connect rules of your firewall.
It helped me with IDEA 14.0.3

Answer 3

I encountered same error when we deploy our application to a Windows Server, however, this server has no antivirus software and the firewall is disabled. In our case, it's due to the Astrill VPN, if we disable the Astrill VPN, the issue would disappear.

Answer 4

My os is Windows, Use Pycharm 2017.3 to run scrapy project encountered a similar problem.
Today, Use Intellij Idea 2016.3.5 to run spring project had the same question.
In my os, Close the Windows Defender can solve this question.

Answer 5

We have to turn off the firewall. It solves the problem. Even in "eclipse" software also turning off the firewall works well.

Answer 6

updating pycharm to a newer version worked for me and then restarting the pycharm ide.