1、在应用程序中调用不同服务时，经常会遇到No route to host程序异常的问题。如下图所示部分日志截取如下：Caused by: java.net.NoRouteToHostException: No route to hostat java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_91]at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_91]at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_91]at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_91]at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_91]at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_91]at java.net.Socket.connect(Socket.java:538) ~[na:1.8.0_91]at sun.net.NetworkClient.doConnect(NetworkClient.java:180) ~[na:1.8.0_91]at sun.net.www.http.HttpClient.openServer(HttpClient.java:432) ~[na:1.8.0_91]at sun.net.www.http.HttpClient.openServer(HttpClient.java:527) ~[na:1.8.0_91]at sun.net.www.http.HttpClient.<init>(HttpClient.java:211) ~[na:1.8.0_91]at sun.net.www.http.HttpClient.New(HttpClient.java:308) ~[na:1.8.0_91]at sun.net.www.http.HttpClient.New(HttpClient.java:326) ~[na:1.8.0_91]at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1169) ~[na:1.8.0_91]
3、登录楫默礤鲼目标服务器，查看防火墙状态：serviceiptablesstatus使用 iptables --list 命令可查看到当前服务器防火墙的配置。（注意：命令使用需要切换至Linux系统Root用户下）
5、最后，在调用的机器上使用telnet 命令验证，发现目标端口可通信，如下图所示。
