Java IP Address Get getIPAddressFromNetworkInterface(String ifaceName)

Description

Returns an InetAddress object encapsulating what is most likely the machine's LAN IP address.

License

Apache License

Parameter

Parameter	Description
ifaceName	The name of the network interface to extract the IP address from

Exception

Parameter	Description
UnknownHostException	If the LAN address of the machine cannot be found.

Declaration

static InetAddress getIPAddressFromNetworkInterface(String ifaceName)
        throws SocketException, UnknownHostException 

Method Source Code

//package com.java2s;
/*//from ww w .  j av a 2  s  .co m
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 {
    /**
     * Returns an <code>InetAddress</code> object encapsulating what is most
     * likely the machine's LAN IP address.
     * <p/>
     * This method is intended for use as a replacement of JDK method
     * <code>InetAddress.getLocalHost</code>, because that method is ambiguous
     * on Linux systems. Linux systems enumerate the loopback network
     * interface the same way as regular LAN network interfaces, but the JDK
     * <code>InetAddress.getLocalHost</code> method does not specify the
     * algorithm used to select the address returned under such circumstances,
     * and will often return the loopback address, which is not valid for
     * network communication. Details
     * <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037">here</a>.
     * <p/>
     * This method will scan all IP addresses on a particular network interface
     * specified as parameter on the host machine to determine the IP address
     * most likely to be the machine's LAN address. If the machine has multiple
     * IP addresses, this method will prefer a site-local IP address (e.g.
     * 192.168.x.x or 10.10.x.x, usually IPv4) if the machine has one (and will
     * return the first site-local address if the machine has more than one),
     * but if the machine does not hold a site-local address, this method will
     * return simply the first non-loopback address found (IPv4 or IPv6).
     * <p/>
     * If this method cannot find a non-loopback address using this selection
     * algorithm, it will fall back to calling and returning the result of JDK
     * method <code>InetAddress.getLocalHost()</code>.
     * <p/>
     *
     * @param ifaceName
     *             The name of the network interface to extract the IP address
     *             from
     * @throws UnknownHostException
     *             If the LAN address of the machine cannot be found.
     */
    static InetAddress getIPAddressFromNetworkInterface(String ifaceName)
            throws SocketException, UnknownHostException {

        NetworkInterface iface = NetworkInterface.getByName(ifaceName);
        if (iface == null) {
            throw new IllegalArgumentException("Network interface " + ifaceName + " not found");
        }

        InetAddress candidateAddress = null;
        Enumeration<InetAddress> inetAddrs = iface.getInetAddresses();
        while (inetAddrs.hasMoreElements()) {
            InetAddress inetAddr = inetAddrs.nextElement();
            if (!inetAddr.isLoopbackAddress()) {
                if (inetAddr.isSiteLocalAddress()) {
                    return inetAddr; // Return non-loopback site-local address
                } else if (candidateAddress == null) {
                    // Found non-loopback address, but not necessarily site-local
                    candidateAddress = inetAddr;
                }
            }
        }

        if (candidateAddress != null) {
            // Site-local address not found, but found other non-loopback addr
            // Server might have a non-site-local address assigned to its NIC
            // (or might be running IPv6 which deprecates "site-local" concept)
            return candidateAddress;
        }

        // At this point, we did not find a non-loopback address.
        // Fall back to returning whatever InetAddress.getLocalHost() returns
        InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();
        if (jdkSuppliedAddress == null) {
            throw new UnknownHostException("InetAddress.getLocalHost() unexpectedly returned null.");
        }
        return jdkSuppliedAddress;
    }
}

Related

1. getIPAddresses()
2. getIpAddresses()
3. getIpAddressesFromNic()
4. getIpAddressExternal()
5. getIPAddressFromBytes(byte[] bytes)
6. getIPAddressFromNetworkInterfaces()
7. getIPAdresses()
8. getIpByHost(String hostName)
9. getIpByHost(String hostName)