How to know programmatically whether a machne is in Global/Private network

Question

I am trying to write a program in Java to know whether a machine is in Global/Private network or not. Below is my code snippet. I thought if a machine detects only loopback address(127.0.0.1 or ::1) then it can be assumed that machine is not in network. But in one of the System where multicast is enabled, I am getting following IP Addresses other than loop back address.

fe80::20c:29ff:fe90:8041
ff01::1,
ff02::1
ff02::1:ff90:8041
fe80::ffff:ffff:fffd
::1
fe80::1
127.0.0.1
224.0.0.1

Code snippet:

private static ArrayList< InetAddress > getInetAddresses( ) throws IPAddressException
    {

        ArrayList< InetAddress > arrayIPAddress = new ArrayList< InetAddress >( );

        try
        {
            Enumeration< NetworkInterface > networkInterfaces = NetworkInterface.getNetworkInterfaces( );

            if ( networkInterfaces == null )
            {
                throw new IPAddressException( "NetworkInterface Not found" );
            }

            while ( networkInterfaces.hasMoreElements( ) )
            {
                NetworkInterface card = ( NetworkInterface ) networkInterfaces.nextElement( );

                Enumeration< InetAddress > addresses = card.getInetAddresses( );

                if ( addresses == null )
                {
                    continue;
                }

                while ( addresses.hasMoreElements( ) )
                {
                    InetAddress inetAddress = ( InetAddress ) addresses.nextElement( );
                    arrayIPAddress.add( inetAddress );

                }
            }
        }
        catch ( SocketException obj )
        {
            throw new IPAddressException( "NetworkInterface Not found" );
        }

        return arrayIPAddress;
    }

IPConfig report:

C:\Documents and Settings\Administrator>ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : vm13autopassdl1
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Unknown
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No
   DNS Suffix Search List. . . . . . : ind.hp.com
                                       india.hp.com

Ethernet adapter Local Area Connection 2:

   Media State . . . . . . . . . . . : Media disconnected
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection #
2
   Physical Address. . . . . . . . . : 00-0C-29-90-80-41

Tunnel adapter Teredo Tunneling Pseudo-Interface:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
   Physical Address. . . . . . . . . : FF-FF-FF-FF-FF-FF-FF-FF
   DHCP Enabled. . . . . . . . . . . : No
   IP Address. . . . . . . . . . . . : fe80::ffff:ffff:fffd%4
   Default Gateway . . . . . . . . . :
   NetBIOS over Tcpip. . . . . . . . : Disabled

Is there any other way to detect whethre machine is not in network?

Answer 1

I would try to see if you can connect to a well-known site on the Internet (e.g., google.com, microsoft.com) using a well-known port (e.g., 80). If you can, then you're on the Internet; if you can't, then you might as well not be. Note that corporate firewall rules could still interfere with whatever you're trying to do -- even if you're on the Internet.

Answer 2

In addition to the loopback addresses 127.0.0.1 and ::1, you should also ignore:

• IPv6 Link-local addresses - these start with fe8, fe9, fea or feb.
• IPv4 Multicast addresses - these start with 224 through to 239.
• IPv6 Multicast addresses - these start with ff.