Android DNS 获取

得到Android 客户端的DNS信息

方法1，运行command得到DNS，（getprop net.dns1/getprop net.dns2）

    private String getLocalDNS(){
        Process cmdProcess = null;
        BufferedReader reader = null;
        String dnsIP = "";
        try {
            cmdProcess = Runtime.getRuntime().exec("getprop net.dns1");
            reader = new BufferedReader(new InputStreamReader(cmdProcess.getInputStream()));
            dnsIP = reader.readLine();
            return dnsIP;
        } catch (IOException e) {
            return null;
        } finally{
            try {
                reader.close();
            } catch (IOException e) {
            }
            cmdProcess.destroy();
        }
    }

方法2，得到WiFiManager，WiFiManager中可以得到wifi的dns，ip等一些网络信息。

    public static Map<String,String> getWifiNetInfo(Context context){
        Map<String,String> wifiInfo = new HashMap<>();
        WifiManager wifi = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        if(wifi  != null){
            DhcpInfo info = wifi.getDhcpInfo();
            wifiInfo.put("wifi-dns", intToIp(info.dns1) + ";" + intToIp(info.dns2));
            wifiInfo.put("wifi-gateway", intToIp(info.gateway));
            wifiInfo.put("wifi-ip", intToIp(info.ipAddress));
            wifiInfo.put("wifi-netmask", intToIp(info.netmask));
            wifiInfo.put("wifi-leaseTime", String.valueOf(info.leaseDuration));
            wifiInfo.put("wifi-dhcpServer", intToIp(info.serverAddress));
        }
        return wifiInfo;
    }

    public static String intToIp(int addr) {
        return  ((addr & 0xFF) + "." +
                ((addr >>>= 8) & 0xFF) + "." +
                ((addr >>>= 8) & 0xFF) + "." +
                ((addr >>>= 8) & 0xFF));
    }

在Android5.1上实验了方法1和方法2，方法2在手机wifi关闭后，dns,gateway,ip,netmask,leaseTime都得不到了，神奇的是dhcpServer竟然有值，实在不解。

方法1在4G/wifi都关闭后，依然可以得到dns信息，表现比较靠谱，推荐使用。