测试IP和端口是否与网络连通

首先搞清楚网络上常用的几个类：

InetAddress表示IP地址，无论是IPV4，还是IPV6，Inet4Address表示IPV4，Inet6Address表示IPV6。SocketAddress表示不依赖于具体协议的套接字地址抽象，InetSocketAddress表示IP地址的套接字地址，包含IP地址和端口号。

代码：

 private static boolean isReachable(InetAddress netAddr, int port, int timeout) {


        boolean isReachable = false;
        Socket socket = null;
        try {
            socket = new Socket(); 
            // Creates a socket address from an IP address and a port number
            InetSocketAddress endpointSocketAddr = new InetSocketAddress(netAddr, port);
            socket.connect(endpointSocketAddr, timeout);
            System.out.println("SUCCESS - remote: " + netAddr.getHostAddress() + " port " + port);
            isReachable = true;
        } catch (IOException e) {
            System.out.println("FAILRE - remote: " + netAddr.getHostAddress() + " port " + port);
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                    System.out.println("Error occurred while closing socket..");
                }
            }
        }
        return isReachable;
    }

参考：http://docs.oracle.com/javase/1.4.2/docs/api/java/net/InetSocketAddress.html