Here you can find the source of getLocalHostID()
Generates an array of 6-bytes that is a fairly reliable identifier of the system on which this code is running.
public final static byte[] getLocalHostID()
//package com.java2s; /*/* w w w .j a v a 2s. c o m*/ * Copyright 2016 Richard Cartwright * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.net.InetAddress; import java.net.NetworkInterface; import java.net.SocketException; import java.net.UnknownHostException; import java.util.Enumeration; public class Main { /** * <p>Generates an array of 6-bytes that is a fairly reliable identifier of the system on * which this code is running. If the an Ethernet address of one of the network interfaces * of this system is available, this is returned. Otherwise, the {@link #createLocalHostID(int)} * method is called to generate a value based on domain name and IP address.</p> * * <p>The value returned is designed to be good enough for time-based UUID generation * within a specific facility or well controlled environment. For rigorous control, * a system administrator should use {@link tv.amwa.maj.industry.Forge#setLocalNodeID(byte[])} * to inject values known to be totally unique.</p> * * @return Fairly good unique identifier for this system. * * @see tv.amwa.maj.industry.Forge#setLocalNodeID(byte[]) * @see tv.amwa.maj.industry.Forge#timebasedAUID() * @see tv.amwa.maj.industry.Forge#generatePackageID(tv.amwa.maj.enumeration.MaterialType, tv.amwa.maj.record.InstanceNumberGeneration, tv.amwa.maj.record.MaterialNumberGeneration) * @see #createLocalHostID(int) */ public final static byte[] getLocalHostID() { try { Enumeration<NetworkInterface> netInterfaces = NetworkInterface.getNetworkInterfaces(); byte[] candidateAddress = null; for (; netInterfaces.hasMoreElements();) { candidateAddress = netInterfaces.nextElement().getHardwareAddress(); if (!suspiciousHardwareAddress(candidateAddress)) break; else candidateAddress = null; } if (candidateAddress != null) return candidateAddress; } catch (SocketException se) { } return createLocalHostID(6); } private final static boolean suspiciousHardwareAddress(byte[] hardwareAddress) { if (hardwareAddress == null) return true; int zeros = 0; for (byte b : hardwareAddress) if (b == 0) zeros++; return (zeros > 2) ? true : false; } /** * <p>Generates a byte array of the given size that should be a value unique to the host * on which the current Java virtual machine is running. Java does not have an API call to * access the unique hardware address of a system, so bytes compatible with an * <a href="http://en.wikipedia.org/wiki/MAC_Address">EUI-48 or EUI-64</a> * <em>locally administered</em> value is generated.</p> * * <p>The four most significant bytes of the generated host id are set to be the four most * significant bytes of the IP address of the current system. The least significant bits of * the value are taken from the most local part of the domain name for the system. This is done * with the intention that locally administered systems on separate private networks within * different organisation should generate different ids.</p> * * <p>If no local network information is available, other local information about the identification * of the machine is used instead. Note that this technique is likely to generate very similar * or clashing host ids for systems configured with the same operating system, Java virtual machine * and username.</p> * * <p>This method is no substitute for administering local system identities directly or using * actual MAC addresses. The method should provide some degree of host id uniqueness within * an organisation but should be used with caution if used as part of a public system or * business-to-business applications. A much better approach is to pass the MAC address of * a system in to a Java virtual machine as a system property, including a unique virtual machine id * if the same system will be running more than one instance of an operating system in parallel.</p> * * @param size Number of bytes or host id required. Values of 6 and 8 are recommended as the only * values likely to produce reasonably reliable results. * @return An array of bytes extracted from some relatively unique properties of the current * system. Using this function on a set of systems on a network controlled by one organisation * should produce unique results for each different system. * * @throws NegativeArraySizeException Cannot create a unique host ID value with a negative array size. * * @see tv.amwa.maj.industry.Forge#setLocalNodeID(byte[]) * @see tv.amwa.maj.industry.Forge#timebasedAUID() * @see tv.amwa.maj.industry.Forge#generatePackageID(tv.amwa.maj.enumeration.MaterialType, tv.amwa.maj.record.InstanceNumberGeneration, tv.amwa.maj.record.MaterialNumberGeneration) * @see #getLocalHostID() */ public final static byte[] createLocalHostID(int size) throws NegativeArraySizeException { if (size < 0) throw new NegativeArraySizeException( "Cannot create a unique host ID value with a negative array size."); byte[] hostAddress = null; String hostname = null; try { InetAddress hostInetAddress = java.net.InetAddress.getLocalHost(); hostAddress = hostInetAddress.getAddress(); hostname = hostInetAddress.getCanonicalHostName(); } catch (UnknownHostException uhe) { hostAddress = new byte[] { System.getProperty("os.version").getBytes()[0], System.getProperty("os.arch").getBytes()[0], System.getProperty("os.name").getBytes()[0], System.getProperty("java.vm.name").getBytes()[0] }; hostname = System.getProperty("user.dir"); } byte[] hostID = new byte[8]; // Try to extract the most local part of the domain name int firstDot = hostname.indexOf('.'); if ((firstDot == -1) || (firstDot >= hostname.length() - 4)) { hostID[0] = (byte) 'x'; hostID[1] = (byte) 'x'; hostID[2] = (byte) 'x'; hostID[4] = (byte) 'x'; } else { byte[] endOfTheDomain = hostname.substring(firstDot + 1, firstDot + 5).getBytes(); System.arraycopy(endOfTheDomain, 0, hostID, 0, 4); } System.arraycopy(hostAddress, hostAddress.length - 4, hostID, 4, 4); // Set the locally administered flag (7th bit of the first byte is 1) and unicast (8th bit of // the first byte is 0). hostID[0] = (byte) ((((int) hostID[0]) & 0xfc) | 2); switch (size) { case 6: byte[] shorter = new byte[6]; shorter[0] = hostID[0]; System.arraycopy(hostID, 3, shorter, 1, 5); return shorter; case 8: return hostID; default: return checkBytes(hostID, size); } } /** * <p>Ensures that an array contains exactly the required number of bytes. If it does not, * it is either padded with 0s to the right to make it up to the required length or truncated * at the required length to make it fit.</p> * * <p>If the array passed in is <code>null</code>, an array of the required length containing 0's * is created.</p> * * @param data Array to check the length of. * @param requiredLength Required length of the array. * @return If the length is OK, a cloned copy of the given array. Otherwise, a replacement array * is created that is a padded or truncated version of the one provided to the required length. * * @throws NegativeArraySizeException The required array length is negative, which is not * allowed for an array length. * * @see tv.amwa.maj.record.PackageID * @see tv.amwa.maj.record.AUID */ public static final byte[] checkBytes(byte[] data, int requiredLength) throws NegativeArraySizeException { if (data == null) data = new byte[0]; if (data.length != requiredLength) { byte[] replacement = new byte[requiredLength]; for (int u = 0; u < requiredLength; u++) replacement[u] = (byte) 0; if (data.length < requiredLength) { for (int u = 0; u < data.length; u++) replacement[u] = data[u]; } else { for (int u = 0; u < requiredLength; u++) replacement[u] = data[u]; } return replacement; } return data.clone(); } }