Steps to reproduce:
1. Download and open attached project "WWW test.zip"
2. Open scene "Test" and play it
3. Notice output in console: "WWW.isDone: true WWW.error: <> WWW.text: <OK>"
4. Turn off internet in a way that is convenient for you
5. Play scene again and notice that WWW.error part in output is empty

Expected result: Console output is "WWW.error: <Failed to connect to 192.121.166.103 port 80: Network unreachable>"

Notes: If WWW connection address is changed to domain name instead of address (e.g. "http://google.com&quot;) error is shown as expected.

Tested and reproduced on:
OSX 10.11
Unity 5.3.3p2, 5.4.0b8

Not reproducible on:
OSX 10.11
5.2.4f1

Windows 10
Unity 5.1.4f1, 5.2.4p1, 5.3.3p3, 5.4.0b10