External communication with sam

[Superpat]

From the man page for plan9port sam(1)

    External communication
      Sam listens to the edit plumb port.  If plumbing is not
      active, on invocation sam creates a named pipe /srv/sam.user
      which acts as an additional source of commands.  Characters
      written to the named pipe are treated as if they had been
      typed in the command window.

I tried plumbing sam commands to plumb/edit and I tried finding something like /srv/sam.user, but without success.

Is there a way to send commands to sam from an external process?