[Zope] connection string to postgresql *socket*

Hi, Since my Postgresql and Zope run on the same box, I would rather like to connect Zope to a postgresql socket than to an open port. I know the connection string to connect to a port is of the form "database@host:port user password" but I cannot find any documentation on the connection string for a socket.. (Zope 2.3.3 on FreeBSD 4.2 with Postgresql 7.1.2 and ZPyGreSQLDA-0-0-3 ) TIA, Reinoud