Linux下防火墙开启相关端口及查看已开启端口

最近利用Apache Mina实现了一个http服务，发布到linux下发现无法访问，通过HttpClient来发送http请求时，报如下错误：

Exception in thread "main" org.apache.http.conn.HttpHostConnectException: Connection to http://10.5.20.96:8011 refused
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:190)
    at org.apache.http.impl.conn.ManagedClientConnectionImpl.open(ManagedClientConnectionImpl.java:294)
    at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:640)
    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:479)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:906)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:1066)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:1044)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:1035)
    at com.tudou.findlabel.entrance.ClientWithResponseHandler.main(ClientWithResponseHandler.java:52)
Caused by: java.net.ConnectException: Connection refused: connect
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
    at java.net.Socket.connect(Socket.java:519)
    at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:127)
    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
    ... 8 more
原来是因为linux下没有开启对8011的端口访问权限造成的。通过下面的命令可以开启允许对外访问的网络端口：

/sbin/iptables -I INPUT -p tcp --dport 8011 -j ACCEPT #开启8011端口 

/etc/rc.d/init.d/iptables save #保存配置 

/etc/rc.d/init.d/iptables restart #重启服务 

查看端口是否已经开放

/etc/init.d/iptables status 

结果如下