public static String getHost() {
        return getHost(null);
    }
@Test
    public void testGetHost() throws Exception {
        // first net card
        Vector<InetAddress> addresses1 = new Vector<>();
        addresses1.add(InetAddress.getByAddress("local-host", new byte[]{(byte) 192, (byte) 168, (byte) 50, (byte) 66}));
        NetworkInterface nic1 = mock(NetworkInterface.class);
        when(nic1.getInetAddresses()).thenReturn(addresses1.elements());
        when(nic1.getName()).thenReturn("local");
        // second net card
        Vector<InetAddress> addresses2 = new Vector<>();
        addresses2.add(InetAddress.getByAddress("eth0-host", new byte[]{(byte) 172, (byte) 168, (byte) 166, (byte) 12}));
        NetworkInterface nic2 = mock(NetworkInterface.class);
        when(nic2.getInetAddresses()).thenReturn(addresses2.elements());
        when(nic2.getName()).thenReturn("eth0");
        // third net card
        Vector<InetAddress> addresses3 = new Vector<>();
        addresses3.add(InetAddress.getByAddress("eth1-host", new byte[]{(byte) 10, (byte) 150, (byte) 111, (byte) 66}));
        NetworkInterface nic3 = mock(NetworkInterface.class);
        when(nic3.getInetAddresses()).thenReturn(addresses3.elements());
        when(nic3.getName()).thenReturn("eth1");
        // add all
        Vector<NetworkInterface> nics = new Vector<>();
        nics.add(nic1);
        nics.add(nic2);
        nics.add(nic3);
        networkInterfaceMockedStatic.when((MockedStatic.Verification) NetworkInterface.getNetworkInterfaces()).thenReturn(nics.elements());
        String prefix1 = "172.168";
        assertEquals("172.168.166.12", IpUtils.getHost(prefix1));
    }