When I tested this last year with draythomp, we got some timeouts because we were hitting it so hard. It appeared to me to be using all 4 then. I had two localnet computers and draythomp hitting it. I would get the "whirly wheel", but always got the "connected" message and eventually a webpage, or the "server not responding" message.
And draythomp was "cheating". He was sending a request and not waiting for the server to respond before sending another request.
I'll try to think of a test.
edit: Keep in mind the public ip was posted here on the forum, so I am sure more than just draythomp and I were on that. For a good percentage of the time, my two computers would both show "connected" and the whirly wheel, and I showed draythomp as the active socket on the serial monitor. Eventually, the computers got a webpage.