有时候插件也会有这样的报错

[16:55:22] [Netty Server IO #1/WARN]: Failed to initialize a channel. Closing: [id: 0xdee33db0, L:/127.0.0.1:10641 - R:/127.0.0.1:55809]
java.lang.NoSuchMethodError: com.google.common.base.Objects.toStringHelper(Ljava/lang/Object;)Lcom/google/common/base/Objects$ToStringHelper;
        at com.comphenix.protocol.events.ListeningWhitelist.toString(ListeningWhitelist.java:241) ~[?:?]
        at java.lang.String.valueOf(Unknown Source) ~[?:1.8.0_111]
        at java.lang.StringBuilder.append(Unknown Source) ~[?:1.8.0_111]
        at com.comphenix.protocol.reflect.PrettyPrinter.printValue(PrettyPrinter.java:273) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:246) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:251) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printValue(PrettyPrinter.java:285) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printValue(PrettyPrinter.java:257) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printIterables(PrettyPrinter.java:144) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printValue(PrettyPrinter.java:277) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:246) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:124) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:102) ~[?:?]
        at com.comphenix.protocol.reflect.PrettyPrinter.printObject(PrettyPrinter.java:89) ~[?:?]
        at com.comphenix.protocol.error.DetailedErrorReporter.getStringDescription(DetailedErrorReporter.java:480) ~[?:?]
        at com.comphenix.protocol.error.DetailedErrorReporter.reportDetailed(DetailedErrorReporter.java:369) ~[?:?]
        at com.comphenix.protocol.error.DelegatedErrorReporter.reportDetailed(DelegatedErrorReporter.java:63) ~[?:?]
        at com.comphenix.protocol.error.DelegatedErrorReporter.reportDetailed(DelegatedErrorReporter.java:87) ~[?:?]
        at com.comphenix.protocol.injector.netty.ProtocolInjector$1.initChannel(ProtocolInjector.java:149) ~[?:?]
        at io.netty.channel.ChannelInitializer.initChannel(ChannelInitializer.java:113) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.ChannelInitializer.handlerAdded(ChannelInitializer.java:105) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.callHandlerAdded0(DefaultChannelPipeline.java:637) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.addLast(DefaultChannelPipeline.java:235) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.addLast(DefaultChannelPipeline.java:409) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.addLast(DefaultChannelPipeline.java:396) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at com.comphenix.protocol.injector.netty.ProtocolInjector$2.initChannel(ProtocolInjector.java:159) [ProtocolLib.jar:4.2.0]
        at io.netty.channel.ChannelInitializer.initChannel(ChannelInitializer.java:113) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.ChannelInitializer.handlerAdded(ChannelInitializer.java:105) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.callHandlerAdded0(DefaultChannelPipeline.java:637) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.access$000(DefaultChannelPipeline.java:46) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline$PendingHandlerAddedTask.execute(DefaultChannelPipeline.java:1487) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.callHandlerAddedForAllHandlers(DefaultChannelPipeline.java:1161) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.invokeHandlerAddedIfNeeded(DefaultChannelPipeline.java:686) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannel$AbstractUnsafe.register0(AbstractChannel.java:510) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannel$AbstractUnsafe.access$200(AbstractChannel.java:423) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannel$AbstractUnsafe$1.run(AbstractChannel.java:482) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:463) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_111]
[16:55:22] [Netty Server IO #1/WARN]: An exception 'java.lang.NullPointerException' [enable DEBUG level for full stacktrace] was thrown by a user handler's exceptionCaught() method while handling the following exception:
java.lang.NullPointerException: null
        at net.minecraft.server.v1_12_R1.NetworkManager.close(NetworkManager.java:250) ~[server.jar:git-Spigot-642f6d2-57ab4cf]
        at net.minecraft.server.v1_12_R1.NetworkManager.channelInactive(NetworkManager.java:106) ~[server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:377) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:342) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java:377) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java:342) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.ChannelInboundHandlerAdapter.channelInactive(ChannelInboundHandlerAdapter.java:75) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.ChannelInboundHandlerAdapter.channelInactive(ChannelInboundHandlerAdapter.java:75) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.handler.timeout.IdleStateHandler.channelInactive(IdleStateHandler.java:277) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java:224) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline$HeadContext.channelInactive(DefaultChannelPipeline.java:1429) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:245) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java:231) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.DefaultChannelPipeline.fireChannelInactive(DefaultChannelPipeline.java:947) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.AbstractChannel$AbstractUnsafe$8.run(AbstractChannel.java:822) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:463) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) [server.jar:git-Spigot-642f6d2-57ab4cf]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_111]

貌似是你检查更新时候卡住了
尝试用这个mod NonUpdate-AllMCVersion-Final-2.0.2-universal.jar (19.43 KB, 下载次数: 1)

建议你先开个1.12.2的端，然后把world、plugins、mods、config都复制过去就行了

这个是我客户端的问题吗？mod的话。。。意思就是说，我用1.12.2的核心重新开个端，然后内容覆盖一遍咯？

这个mod是干嘛用的？

对，不过应该不是客户端问题，那个报错里包含了value（或者更新下这个插件？

你用的ProtocolLib应该不支持1.12.2了
ProtocolLib更换这个版本:
ProtocolLib.jar (1.37 MB, 下载次数: 1)

我去试试

首先备份
然后确保插件均兼容1.12.2
地图1.11.2能用1.12.2就能用
其他没有要准备

wocao 牛逼！

问题解决了，谢谢大家的帮助

加一下跨版本不就可以了吗，为何非得升级核心？

插件兼容

不兼容1.11？