postmaster generates no socket

Hi

I can start postmaster, but it does not generate a socket.
I startet the postmaster with -i,
in postgresql.conf I set tcpip_socket=true
unix_socket_directory = '/tmp'
in pg_hba.conf I set the server's and the client's ip-address to trust.

The attempt to connect via PHP4 results in the mesage:
Warning: Unable to connect to PostgreSQL server: could not connect to server: No such file or directory Is the server
runninglocally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?  
Why does it expect the socket in /var/run/postgresql/ and why does the Postmaster not create any socket at all?

Thanks very much

Christoph Della Valle