Postgres Connection with postmaster

Hi,

Can you tell me how the Postmaster communicates with postgres database
functions like Createdb, Destroydb, and createuser etc..

As i am trying to establish a connection betn postmaster & postgres but
everytime
following message is coming
createdb: not found
destroydb:not found

FATAL: StreamOpen: connect() failed:errno=146
FATAL: Failed to connect to postmaster (host=localhost, port=4321)
      Is the postmaster running?

so pls help me as i couldn't create a connection of postmaster & postgres..

thanks for help in advance..
bye
Dinesh