the game crashes every time i want to play in a world (single payer and multyplayer)

Incomplete without a crash report from ([minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/finding-minecraft-data-folder]). Please attach it so that we can diagnose your issue.

For technical support please use the Mojang Support Center.

in the description?

Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 30/04/15 19.21
Description: Updating screen events

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 rd.a(SourceFile:40)
at rd.b(SourceFile:37)
at up.c(SourceFile:10)
at rc.a(SourceFile:104)
at bsu.a(SourceFile:1914)
at bxg.i(SourceFile:172)
at bxh.a(SourceFile:224)
at bvk.p(SourceFile:309)
at bxg.k(SourceFile:82)
at bxf.p(SourceFile:382)
at bsu.r(SourceFile:1473)
at bsu.as(SourceFile:877)
at bsu.a(SourceFile:314)
at net.minecraft.client.main.Main.main(SourceFile:120)
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)
... 17 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:126)
... 20 more
Caused by: java.io.IOException: Connessione in corso interrotta forzatamente dall'host remoto
at sun.nio.ch.SocketDispatcher.read0(Native Method)
at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
at sun.nio.ch.IOUtil.read(IOUtil.java:197)
at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:379)
at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:139)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
... 28 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 rd.a(SourceFile:40)
at rd.b(SourceFile:37)
at up.c(SourceFile:10)
at rc.a(SourceFile:104)
at bsu.a(SourceFile:1914)
at bxg.i(SourceFile:172)
at bxh.a(SourceFile:224)
at bvk.p(SourceFile:309)
at bxg.k(SourceFile:82)
at bxf.p(SourceFile:382)

– Affected screen –
Details:
Screen name: bxq
Stacktrace:
at bsu.r(SourceFile:1473)
at bsu.as(SourceFile:877)
at bsu.a(SourceFile:314)
at net.minecraft.client.main.Main.main(SourceFile:120)

– System Details –
Details:
Minecraft Version: 1.8
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 191802864 bytes (182 MB) / 632291328 bytes (603 MB) up to 3817865216 bytes (3641 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx4G
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.8
LWJGL: 2.9.1
OpenGL: GeForce GTX 745/PCIe/SSE2 GL version 4.4.0, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)

Duplicate of MC-34749. Something, like your antivirus or firewall software, is blocking java.

This is a technical support issue; this site is for bug reports only. For technical support please use the Mojang Support Center.