<li>Open Transmission, go to Preferences >> Network and enter a number for the port. It is recommended you pick a random number between 49152 and 65535. Let's use 50001 for now. Then quit Transmission. </li>
<li>Open System Prefs >> Sharing >> Firewall. Click "New." In the "Port Name" pop-up menu, select Other, and fill in the settings as follows: </li>
<ul>
<li>TCP Port Number(s): the port you chose in step 1 - eg 50001. </li>
<li>UDP Port Number(s): the port you chose in step 1 - eg 50001. </li>
<p>Upon opening Transmission for the first time, a Mac OS X dialogue box should appear asking if you will allow Transmission to receive incoming connections. Click Accept.
<p>If this doesn't happen, you can add Transmission to Leopard's firewall manually:
<divsummary="To do this"id="taskbox">
<ol>
<li>Open System Prefs >> Security >> Firewall. Make sure "Set access for specific services and applications" is selected.</li>
<li>Click the "+" button and select Transmission from you Applications folder. </li>
<li>Make sure the pull down menu is set to "Allow incoming connections".