Java Local Address Get getLocalAddress()

Description

Get a local, IP4 Address, preferable a non-loopback address which is bound to an interface.

License

Apache License

Exception

Parameter	Description
UnknownHostException	an exception
SocketException	an exception

Declaration

public static InetAddress getLocalAddress() throws UnknownHostException, SocketException 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.*;
import java.util.*;

public class Main {
    private static Method isUp;
    private static Method supportsMulticast;

    /**/*from www . j  a v a2  s.  c o m*/
     * Get a local, IP4 Address, preferable a non-loopback address which is bound to an interface.
     *
     * @return
     * @throws UnknownHostException
     * @throws SocketException
     */
    public static InetAddress getLocalAddress() throws UnknownHostException, SocketException {
        InetAddress addr = InetAddress.getLocalHost();
        NetworkInterface nif = NetworkInterface.getByInetAddress(addr);
        if (addr.isLoopbackAddress() || addr instanceof Inet6Address || nif == null) {
            // Find local address that isn't a loopback address
            InetAddress lookedUpAddr = findLocalAddressViaNetworkInterface();
            // If a local, multicast enabled address can be found, use it. Otherwise
            // we are using the local address, which might not be what you want
            addr = lookedUpAddr != null ? lookedUpAddr : InetAddress.getByName("127.0.0.1");
        }
        return addr;
    }

    public static InetAddress findLocalAddressViaNetworkInterface() {
        Enumeration<NetworkInterface> networkInterfaces;
        try {
            networkInterfaces = NetworkInterface.getNetworkInterfaces();
        } catch (SocketException e) {
            return null;
        }

        while (networkInterfaces.hasMoreElements()) {
            NetworkInterface nif = networkInterfaces.nextElement();
            for (Enumeration<InetAddress> addrEnum = nif.getInetAddresses(); addrEnum.hasMoreElements();) {
                InetAddress interfaceAddress = addrEnum.nextElement();
                if (useInetAddress(nif, interfaceAddress)) {
                    return interfaceAddress;
                }
            }
        }
        return null;
    }

    private static boolean useInetAddress(NetworkInterface networkInterface, InetAddress interfaceAddress) {
        return checkMethod(networkInterface, isUp) && checkMethod(networkInterface, supportsMulticast) &&
        // TODO: IpV6 support
                !(interfaceAddress instanceof Inet6Address) && !interfaceAddress.isLoopbackAddress();
    }

    private static Boolean checkMethod(NetworkInterface iface, Method toCheck) {
        if (toCheck != null) {
            try {
                return (Boolean) toCheck.invoke(iface, (Object[]) null);
            } catch (IllegalAccessException e) {
                return false;
            } catch (InvocationTargetException e) {
                return false;
            }
        }
        // Cannot check, hence we assume that is true
        return true;
    }
}

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