在Java中使用IP地址查找mac地址

Question

public static void main(String[] args) {
    try {
        InetAddress address = InetAddress.getLocalHost();
        // InetAddress address = InetAddress.getByName("192.168.46.53");

        /*
         * Get NetworkInterface for the current host and then read the
         * hardware address.
         */
        NetworkInterface ni = NetworkInterface.getByInetAddress(address);
        if (ni != null) {
            byte[] mac = ni.getHardwareAddress();
            if (mac != null) {
                /*
                 * Extract each array of mac address and convert it to hexa with the
                 * following format 08-00-27-DC-4A-9E.
                 */
                for (int i = 0; i < mac.length; i++) {
                    System.out.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : "");
                }
            } else {
                System.out.println("Address doesn't exist or is not accessible.");
            }
        } else {
            System.out.println("Network Interface for the specified address is not found.");
        }

I'm having a problem finding the MAC address of a remote host, but I am able to find the MAC address of my local host. If I have the IP address of the other system can I retrieve the MAC address of that system?

InetAddress address = InetAddress.getByName("192.168.46.53");

if i specify the ip address of a system in my workgroup... ni values gets null.... and not able to fetch it.... but if give my ip address of my system...it fetches???

Thanks,
Sunny

Answer 1

You will only be able to fetch the MAC address of remote hosts on your local LAN, that is, hosts that are in the same subnet as your computer. MAC addresses of hosts more than one hop away (IP hop, not Ethernet hop) cannot be determined.

And note that fetching the corresponding MAC address for hosts on your local LAN requires the permissions necessary to fetch either the ARP table, or those necessary to send and receive raw packets. Most OSes allow reading of the ARP table without special permissions, but the mechanism you use to do so will change depending on the OS. If you need a technique for a particular OS, you will have to update your question to include that info.