Need to identify local machine somehow in java

Question

I'm trying to find out the name of the local machine (or some other way of uniquely identifying a particular machine) that an application is running on.

I've been using this:

String hostname = java.net.InetAddress.getLocalHost().getHostName();

which works fine, but I just happened to notice in the profiler that it's taking quite a bit of time to execute that so I was wondering if there was something functionally similar that ran more quickly.

Doesn't have to be host name, could be anything as long as it uniquely identifies the machine.

score 5 · Answer 1 · edited Mar 01 '12 at 10:24

5

To uniquely identify a machine, I would use the systems MAC address using getHardwareAddress().

However, I'm not sure if that would be any faster - but it would definitely be a better way of uniquely identifying the machine.

For an example, see: http://www.java2s.com/Code/Java/Network-Protocol/GetMACaddressofahostjavanetNetworkInterfacegetHardwareAddress.htm

edited Mar 01 '12 at 10:24

bluish

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answered May 17 '11 at 16:25

Joseph Redfern

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The code you linked fails for me. The localhost address typically doesn't have a network interface or MAC address associated with it. – ataylor May 17 '11 at 16:52
getLocalHost(); returns all of the IP addresses associated with the machine. I don't think that it typically returns the loopback address (127.0.0.1), but usually your internal network address (as in.. 10.0.x.x or 192.168.x.x). I guess you should make it go through each address and discount the 127.0.0.1 entry... – Joseph Redfern May 17 '11 at 17:01
getLocalHost() only returns one address, which will typically be the loopback address on Linux: [http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037](http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037). – ataylor May 17 '11 at 17:55

ataylor · Answer 2 · 2011-05-18T02:12:58.797

2

You could grab the MAC address of the machine. Here's an example of how to get it.

byte[] mac = null;
List<NetworkInterface> interfaces = 
    (List<NetworkInterface>) Collections.list(NetworkInterface.getNetworkInterfaces());
for (NetworkInterface iface: interfaces) {
    if (!iface.isLoopback()) {
        mac = iface.getHardwareAddress();
        if (mac != null) {
            break;
        }
    }
}

This code grabs the MAC address off the first interface that has one. In addition to loopback interfaces, some machines might also have virtual interfaces for VPNs that won't have hardware addresses associated with them.

edited May 18 '11 at 02:12

answered May 17 '11 at 16:37

ataylor

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Superficial changes: 'interface' is a reserved word ;) and the method returns the clunky Enumeration hasNext()/nextElement() thingy. – karmakaze May 18 '11 at 01:07

score 1 · Answer 3 · answered May 17 '11 at 16:23

1

Tried getHostAddress()? From the docs, it seems that getHostName() involves a security check first (if there is a SecurityManager), which means one more method call.

answered May 17 '11 at 16:23

asgs

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score 0 · Answer 4 · answered May 08 '13 at 13:41

Just to save the next person from stumbling over the incomplete MAC retrieval code, here is my version that works on my Windows 7 machine as well as other computers. Note that the code may still return different MACs on each invocation in case the user messed with his hardware and the network devices might be returned in different order.

private static final String generateHashIdentifier() throws Exception {
    Enumeration<NetworkInterface> networkInterfaces
        = NetworkInterface.getNetworkInterfaces();
    while (networkInterfaces.hasMoreElements()) {
        NetworkInterface networkInterface = networkInterfaces.nextElement();
        if (networkInterface == null
            || networkInterface.isLoopback()
            || networkInterface.isVirtual()) {
                continue;
        }
        byte[] mac = networkInterface.getHardwareAddress();
        if (mac == null || mac.length == 0)
            continue;

        StringBuilder sb = new StringBuilder();
        int zeroFieldCount = 0;
        for (int i = 0; i < mac.length; i++) {
            if (mac[i] == 0)
                zeroFieldCount++;
            sb.append(String.format("%02X%s", mac[i],
                (i < mac.length - 1) ? "-" : ""));
        }

        if (zeroFieldCount > 4)
            continue;

        return sb.toString();
    }

    throw new RuntimeException("Failed to obtain MAC");
}

In Windows I get tons of additional devices which may or may not return a NULL mac or a mac with mostly zeros. The code tries to find the first device that gives a reasonable MAC and returns it as a nice String as a bonus.

score 0 · Accepted Answer · edited Mar 01 '12 at 10:24

I came up with this:

String dirname = Utils.safetrim(System.getProperty("user.dir"));

It obviously doesn't world uniquely identify a machine but for my purposes it's good enough, because each person running this program will be logged in as themselves and probably be running from their home directory, so it makes the response unique enough for me.

And of course it's wicked fast, which is the important part.

Need to identify local machine somehow in java

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