Client cant connect to AMS using default Adobe fallback mechanism.

I have a recording application (as3 client) that connects to my AMS instance using port 1935 by default. According to the Adobe documentation (Adobe Media Server 5.0.7 * Configure ports), if the client can't connect to the server using port 1935 then the client by itself uses port 80(rtmp and then rtmpt) to make a connection to the server.

Now, if I block port 1935 on my Ubuntu machine then the request from port 1935 fails . But what's strange is that now my client can't connect using port 80 by the default mechanism that Adobe documents claims is in place.

So, I have put in place my fallback mechanism in my recording AS3 client. Whenever, I get a "Netconnection.Connection.Failed" event I change the connecting url to switch over to "rtmpt" using port 80.This fallback mechanism works perfectly. But the default fallback is taking too much of time which is leading to a bad user-experience.

My question is that whether we have to make some changes at the server or client end to make the default Adobe fallback mechanism work?