Oracle Enterprise Manager DB Console Unavailable

We had this problem a good few weeks ago – we were happily using OEM DB Console and then all of a sudden it was unavailable!
The URL was the same and there was nothing that had changed to our knowledge. Several of us here spent some time and looked around to no avail. It was suggested that another service had taken the port and that is was no longer available for OEM.
As part of investigation I had used netstat -an | grep -i LISTEN to check whether the port was being used and it wasn’t. Strange…
A colleague pointed me in the direction of an Oracle Installation Guide and the section “Managing Oracle Database Port Numbers”. It was while looking through this checking the numbers that I found the problem.
$ORACLE_HOME\install\emd.properties has the EMD_URL property it was here that problem was identified. The URL looked fine at first glance but then I noticed the port number was missing e.g. http://:/emd/main.
So I edited the file in vi and inserted the port number that we had been using. After this I issued the start commmand emctl dbconsole start which kicked off. Then I checked netstat -an | grep -i LISTEN again and to my delight 1158 was there. After a moment or two emctl had completed the dbconsole start with no problems so I eagerly went back to IE and hit up the OEM DB Console – it was there!!
What a great result that is, we had been without it for what seemed like ages, it made me appreciate how much I used and relied on it!