版本：nacos-server-1.1.3
(1).我在自己开发机器: win10，上面运行注册中心

d:\nacos\bin\startup.cmd -m standalone &

有4个服务链接该注册中心，链接是正常的

(2).我在自己的虚拟机: Centos 7.5，上面运行注册中心

/usr/local/nacos/bin/startup.sh -m -standalone &

4个服务链接该注册中心，链接是正常的，启动完毕之后过了3，5分钟，那4给微服务的控制台会出现如下错误：

2019-11-11 17:08:32 ERROR [gateway-center,,,] ThreadPoolTaskScheduler-1 org.springframework.cloud.alibaba.nacos.discovery.NacosWatch Error watching Nacos Service change
java.lang.IllegalStateException: failed to req API:/nacos/v1/ns/service/list after all servers([nacos.cc:6300]) tried: failed to req API:http://nacos.cc:6300/nacos/v1/ns/service/list. code:500 msg: java.net.SocketTimeoutException: connect timed out
	at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:380)
	at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:346)
	at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:294)
	at com.alibaba.nacos.client.naming.net.NamingProxy.getServiceList(NamingProxy.java:276)
	at com.alibaba.nacos.client.naming.net.NamingProxy.getServiceList(NamingProxy.java:252)
	at com.alibaba.nacos.client.naming.NacosNamingService.getServicesOfServer(NacosNamingService.java:525)
	at org.springframework.cloud.alibaba.nacos.discovery.NacosWatch.nacosServicesWatch(NacosWatch.java:127)
	at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)