自己再学习springclooud的时候，刚开始使用eureka服务注册中心，记录一下第一个错误

springcloud在运行服务端的时候出现错误

com.netflix.discovery.shared.transport.TransportException: Cannot execute request on any known server
	at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:112) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:876) ~[eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.10.16.jar:1.10.16]
	at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.10.16.jar:1.10.16]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_311]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_311]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_311]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_311]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_311]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_311]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_311]

问题出现的原因是springcloud的服务注册中心在启动的时候需要在客户端和服务端都需要配置连接eureka的服务端地址，才开始学，自己认为服务端不需要配置服务端地址就有了这个报错。

解决办法：
在配置文件中添加这个配置就可以解决

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:9001/eureka