首页 > 代码库 > 详谈再论JAVA获取本机IP地址

详谈再论JAVA获取本机IP地址

首先,你如果搜索“JAVA获取本机IP地址”,基本上搜到的资料全是无用的。
比如这篇:http://www.cnblogs.com/zrui-xyu/p/5039551.html
实际上的代码在复杂环境下是不准的


网上一个比较普遍的说法是InetAddress.getLocalHost().getHostAddress()
似乎很简单,但忽略了一个问题,即IP地址在现在的网络环境更加复杂了,比如有Lan,WIFI,蓝牙热点,虚拟机网卡...
即存在很多的网络接口(network interfaces),每个网络接口就包含一个IP地址,并不是所有的IP地址能被外部或局域网访问,比如说虚拟机网卡地址等等。
也就是说InetAddress.getLocalHost().getHostAddress()的IP不一定是正确的IP。

写代码前,先明确一些规则:

  • 127.xxx.xxx.xxx 属于"loopback" 地址,即只能你自己的本机可见,就是本机地址,比较常见的有127.0.0.1;
  • 192.168.xxx.xxx 属于private 私有地址(site local address),属于本地组织内部访问,只能在本地局域网可见。同样10.xxx.xxx.xxx、从172.16.xxx.xxx 到 172.31.xxx.xxx都是私有地址,也是属于组织内部访问;
  • 169.254.xxx.xxx 属于连接本地地址(link local IP),在单独网段可用
  • 从224.xxx.xxx.xxx 到 239.xxx.xxx.xxx 属于组播地址
  • 比较特殊的255.255.255.255 属于广播地址
  • 除此之外的地址就是点对点的可用的公开IPv4地址

 

获取本机IP地址的正确姿势:

package ipTest;import java.net.Inet4Address;import java.net.InetAddress;import java.net.NetworkInterface;import java.net.SocketException;import java.net.UnknownHostException;import java.util.Enumeration;public class Test {    public Test() {        // TODO Auto-generated constructor stub    }    public static void main(String[] args) {        // TODO Auto-generated method stub        InetAddress ip;        try {            // 这种IP容易拿错            // System.out.println("Current IP address : " +            // InetAddress.getLocalHost().getHostAddress());            // 不一定准确的IP拿法            // 出自比如这篇:http://www.cnblogs.com/zrui-xyu/p/5039551.html            System.out.println("get LocalHost Address : " + getLocalHostAddress().getHostAddress());            // 正确的IP拿法            System.out.println("get LocalHost LAN Address : " + getLocalHostLANAddress().getHostAddress());        } catch (UnknownHostException e) {            e.printStackTrace();        }    }    // 正确的IP拿法,即优先拿site-local地址    private static InetAddress getLocalHostLANAddress() throws UnknownHostException {        try {            InetAddress candidateAddress = null;            // 遍历所有的网络接口            for (Enumeration ifaces = NetworkInterface.getNetworkInterfaces(); ifaces.hasMoreElements();) {                NetworkInterface iface = (NetworkInterface) ifaces.nextElement();                // 在所有的接口下再遍历IP                for (Enumeration inetAddrs = iface.getInetAddresses(); inetAddrs.hasMoreElements();) {                    InetAddress inetAddr = (InetAddress) inetAddrs.nextElement();                    if (!inetAddr.isLoopbackAddress()) {// 排除loopback类型地址                        if (inetAddr.isSiteLocalAddress()) {                            // 如果是site-local地址,就是它了                            return inetAddr;                        } else if (candidateAddress == null) {                            // site-local类型的地址未被发现,先记录候选地址                            candidateAddress = inetAddr;                        }                    }                }            }            if (candidateAddress != null) {                return candidateAddress;            }            // 如果没有发现 non-loopback地址.只能用最次选的方案            InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();            if (jdkSuppliedAddress == null) {                throw new UnknownHostException("The JDK InetAddress.getLocalHost() method unexpectedly returned null.");            }            return jdkSuppliedAddress;        } catch (Exception e) {            UnknownHostException unknownHostException = new UnknownHostException(                    "Failed to determine LAN address: " + e);            unknownHostException.initCause(e);            throw unknownHostException;        }    }    //出自这篇:http://www.cnblogs.com/zrui-xyu/p/5039551.html    //实际上的代码是不准的    private static InetAddress getLocalHostAddress() throws UnknownHostException {        Enumeration allNetInterfaces;        try {            allNetInterfaces = NetworkInterface.getNetworkInterfaces();            InetAddress ip = null;            while (allNetInterfaces.hasMoreElements()) {                NetworkInterface netInterface = (NetworkInterface) allNetInterfaces.nextElement();                Enumeration addresses = netInterface.getInetAddresses();                while (addresses.hasMoreElements()) {                    ip = (InetAddress) addresses.nextElement();                    if (!ip.isSiteLocalAddress() && !ip.isLoopbackAddress() && ip.getHostAddress().indexOf(":") == -1) {                        if (ip != null && ip instanceof Inet4Address) {                            return ip;                        }                    }                }            }        } catch (SocketException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();        if (jdkSuppliedAddress == null) {            throw new UnknownHostException("The JDK InetAddress.getLocalHost() method unexpectedly returned null.");        }        return jdkSuppliedAddress;    }}

 

详谈再论JAVA获取本机IP地址