Do you want to enable project, web or iPhone sharing on your Merlin and get an error message, that the ports are already used?

Could it be that you are trying to enable project sharing on top of a running Merlin Server? In this case, simply copy the project file in the shared folder of Merlin Server for it it be shared.

Even thought it is possible to have two Merlin Sharing Services on your mac. One over the Merlin Server Mac OS X preference pane and another over your Merlin Mac OS X application. This is not a recommended situation.

If another service, another application on your Mac is using this port, and you really need this service simply define another port number for Merlin Sharing  in Merlin Preferences.

Call Merlin > Preferences…> Sharing tab…

…and enter another port number higher than 1024*.

To edit the TCP ports in Merlin Server, unlock the preference pane (A) first, stop its service (B), and edit the according field (C) finally.

*) For more information about tcp ports, please check this wikipedia article.