The example in this article describes how Java determines whether an IP address is an intranet IP or a public IP. Share it with everyone for your reference. The specific analysis is as follows:
In the TCP/IP protocol, three IP address areas are specially reserved as private addresses. The address ranges are as follows:
10.0.0.0/8：10.0.0.0～10.255.255.255
172.16.0.0/12：172.16.0.0～172.31.255.255
192.168.0.0/16：192.168.0.0～192.168.255.255
So, let’s go straight to the code:
Copy the code as follows: public static boolean internalIp(String ip) {
byte[] addr = IPAddressUtil.textToNumericFormatV4(ip);
return internalIp(addr);
}
public static boolean internalIp(byte[] addr) {
final byte b0 = addr[0];
final byte b1 = addr[1];
//10.xxx/8
final byte SECTION_1 = 0x0A;
//172.16.xx/12
final byte SECTION_2 = (byte) 0xAC;
final byte SECTION_3 = (byte) 0x10;
final byte SECTION_4 = (byte) 0x1F;
//192.168.xx/16
final byte SECTION_5 = (byte) 0xC0;
final byte SECTION_6 = (byte) 0xA8;
switch (b0) {
case SECTION_1:
return true;
case SECTION_2:
if (b1 >= SECTION_3 && b1 <= SECTION_4) {
return true;
}
case SECTION_5:
switch (b1) {
case SECTION_6:
return true;
}
default:
return false;
}
}
I hope this article will be helpful to everyone’s Java programming.