Return the contact info of PROCESS; t for a real child.
For a network or serial connection, the value depends on the optional
KEY arg. If KEY is nil, value is a cons cell of the form (HOST
SERVICE) for a network connection or (PORT SPEED) for a serial
connection. If KEY is t, the complete contact information for the
connection is returned, else the specific value for the keyword KEY is
returned. See `make-network-process' or `make-serial-process' for a
list of keywords. (fn PROCESS &optional KEY)