Failed to bind NettyServer on /192.168.**.*:20880, cause: Failed to bind to: /0.0.0.0:20880

今天遇到的Dubbo的问题，第一天创建项目，在做Dubbo的Demo的时候遇到的问题，这个问题和解决方案，详见下面：

问题：

 Failed to bind NettyServer on /192.168.56.1:20880, cause: Failed to bind to: /0.0.0.0:20880
	at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol.createServer(DubboProtocol.java:289)
	at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol.openServer(DubboProtocol.java:266)
	at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol.export(DubboProtocol.java:253)
	at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper.export(ProtocolFilterWrapper.java:55)
	at com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper.export(ProtocolListenerWrapper.java:56)
	at com.alibaba.dubbo.rpc.Protocol$Adpative.export(Protocol$Adpative.java)
	at com.alibaba.dubbo.registry.integration.RegistryProtocol.doLocalExport(RegistryProtocol.java:153)
	at com.alibaba.dubbo.registry.integration.RegistryProtocol.export(RegistryProtocol.java:107)
	at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper.export(ProtocolFilterWrapper.java:53)
	at com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper.export(ProtocolListenerWrapper.java:54)
	at com.alibaba.dubbo.rpc.Protocol$Adpative.export(Protocol$Adpative.java)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrlsFor1Protocol(ServiceConfig.java:485)
	at com.alibaba.dubbo.config.ServiceConfig.doExportUrls(ServiceConfig.java:281)
	at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:242)
	at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:143)
	at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:109)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:163)
	at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:136)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:381)
	at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:335)
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:855)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)
	at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:93)
	at com.tgb.qmx.demo.dubbo.provider.Provider.main(Provider.java:8)
Caused by: com.alibaba.dubbo.remoting.RemotingException: Failed to bind NettyServer on /192.168.56.1:20880, cause: Failed to bind to: /0.0.0.0:20880
	at com.alibaba.dubbo.remoting.transport.AbstractServer.(AbstractServer.java:72)
	at com.alibaba.dubbo.remoting.transport.netty.NettyServer.(NettyServer.java:63)
	at com.alibaba.dubbo.remoting.transport.netty.NettyTransporter.bind(NettyTransporter.java:33)
	at com.alibaba.dubbo.remoting.Transporter$Adpative.bind(Transporter$Adpative.java)
	at com.alibaba.dubbo.remoting.Transporters.bind(Transporters.java:48)
	at com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchanger.bind(HeaderExchanger.java:41)
	at com.alibaba.dubbo.remoting.exchange.Exchangers.bind(Exchangers.java:63)
	at com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol.createServer(DubboProtocol.java:287)
	... 24 more
Caused by: org.jboss.netty.channel.ChannelException: Failed to bind to: /0.0.0.0:20880
	at org.jboss.netty.bootstrap.ServerBootstrap.bind(ServerBootstrap.java:303)
	at com.alibaba.dubbo.remoting.transport.netty.NettyServer.doOpen(NettyServer.java:94)
	at com.alibaba.dubbo.remoting.transport.AbstractServer.(AbstractServer.java:67)2016-08-07 21:47:25,015 INFO [com.alibaba.dubbo.config.AbstractConfig] -  [DUBBO] Run shutdown hook now., dubbo version: 2.5.3, current host: 127.0.0.1

下面的错误：

Caused by: java.net.BindException: Address already in use: bind
	at sun.nio.ch.Net.bind0(Native Method)
	at sun.nio.ch.Net.bind(Net.java:414)
	at sun.nio.ch.Net.bind(Net.java:406)
	at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:214)
	at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
	at org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.bind(NioServerSocketPipelineSink.java:148)
	at org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.handleServerSocket(NioServerSocketPipelineSink.java:100)
	at org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink.eventSunk(NioServerSocketPipelineSink.java:74)
	at org.jboss.netty.channel.Channels.bind(Channels.java:468)
	at org.jboss.netty.channel.AbstractChannel.bind(AbstractChannel.java:192)
	at org.jboss.netty.bootstrap.ServerBootstrap$Binder.channelOpen(ServerBootstrap.java:348)
	at org.jboss.netty.channel.Channels.fireChannelOpen(Channels.java:176)
	at org.jboss.netty.channel.socket.nio.NioServerSocketChannel.(NioServerSocketChannel.java:85)
	at org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory.newChannel(NioServerSocketChannelFactory.java:142)
	at org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory.newChannel(NioServerSocketChannelFactory.java:90)
	at org.jboss.netty.bootstrap.ServerBootstrap.bind(ServerBootstrap.java:282)
	... 33 more

其实，我们看代码的话，就可以看到，是地址别占用的问题，我们使用的端口号是20880，说明，20880端口已经被占用了。

解决方案：

我们看Zookeeper的注册中心查找到了已经有提供者占用了20880端口：

我们发布一个系统，那么该系统的所有的提供者，就占用了20880端口：

因此，如果我们，再写一个系统，该系统的dubbo-provider中写的20880：

这个时候，就会报上面的错误，也就是20880端口被一个系统已经占用了，因此，这个提供者的端口，就要换一个了，换一个就随便一个没有被占用的端口就可以了：

这样，我们运行一下provider就不会报错了：

我们可以看一下，我们刚刚的两个系统：

在开发环境上是这样的：

总结：

一句话，一个系统一个端口号。