connect timed out

java.net.SocketTimeoutException: connect timed out

at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)

at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)

at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)

at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)

at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)

at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)

at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)

at java.net.Socket.connect(Socket.java:589)

at sun.net.NetworkClient.doConnect(NetworkClient.java:175)

at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)

at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)

at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)

at sun.net.www.http.HttpClient.New(HttpClient.java:339)

at sun.net.www.http.HttpClient.New(HttpClient.java:357)

at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1220)

at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1156)

at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050)

at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:984)

at com.alibaba.nacos.client.naming.net.HttpClient.request(HttpClient.java:86)

at com.alibaba.nacos.client.naming.net.NamingProxy.callServer(NamingProxy.java:433)

at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:468)

at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:401)

at com.alibaba.nacos.client.naming.net.NamingProxy.sendBeat(NamingProxy.java:343)

at com.alibaba.nacos.client.naming.beat.BeatReactor$BeatTask.run(BeatReactor.java:108)

at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)

at java.util.concurrent.FutureTask.run(FutureTask.java:266)

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)

at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)

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)

这个异常是什么意思