Sidney,
The best way to do this is to set a port scan to find all open ports on your server.
One that I use is by Necrosoft called NScan, which you can download from here:
http://nscan.hypermart.net/?index=downloadIf you use this, you need to start NScan and select 'Single Host' instead of 'Host Range' (The top-left drop-down box) and put in the local IP of your server in the 'Initial host' text box, then click Start (In the top-right corner of NScan)
You can either select which ports you want to scan, or have it scan a pre-defined list.
Hope this helps.
Simon