gistfile1.java

    public static byte[] getWifiHostAddress(Context context) {
        WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        DhcpInfo dhcp = wifiManager.getDhcpInfo();

        int host = (dhcp.ipAddress & ~dhcp.netmask);
        
        byte[] quads = new byte[4];
        for (int k = 0; k < 4; k++) {
            quads[k] = (byte) ((host >> k * 8) & 0xFF);
        }
        return quads;
    }
    
    public static String getWifiHostAddressBase64(Context context) {
        byte[] address = getWifiHostAddress(context);
        
        List<Byte> input = new ArrayList<Byte>();
        for (byte segment : address) {
            if (segment > 0) {
                input.add(segment);
            }
        }
        
        byte[] inputBytes = new byte[input.size()];
        
        for (int i = 0; i < inputBytes.length; i++) {
            inputBytes[i] = input.get(i);
        }
        
        return Base64.encodeToString(inputBytes, Base64.DEFAULT).trim();
    }
    
    public static int decodeWifiHostAddressBase64(String base64Str) {
        byte[] bytes = Base64.decode(base64Str, Base64.DEFAULT);
        Slog.d(Arrays.toString(bytes));
        final int length = bytes.length;
        int host = 0;
        for (int i = 0; i < 4; i++) {
            if (i < bytes.length) {
                host = (host << 8) | bytes[length - i];
            } else {
                host = (host << 8);
            }
        }
        return host;
    }