HP OpenVMS Systems

Ask the Wizard Questions

DCL: Access a modem

The Question is:

Is there a DCL way to talk to a modem hanging off a
serial port on a VAXstation? I need to write some code
that will sequentially dial a series of numbers, wait
for answer, check for correct response from, hang up
and then go to the next modem.  I know I can manually
do this with the SET HOST/DTE TTA2.

Thanks

The Answer is:

    	The following should get you started.

    $ open/read/write modem	_tta0:
    $ write modem "ATDT ''number'"
    $ read modem response
    $ close modem

    	You need to add the logic to check the response move on to the next
    number etc.  You should be able to dial, hang up, and read messages
    from the modem with no problems.  Doing real data communications this
    will leave you a little short.

      I like to use a timeout on the READ and a read loop to handle
    multi line responses. Here's part of a command procedure I use to
    dial out. Of course, you could quieten it down a bit by removing the
    SHOW SYMBOL commands, but I like to see what's going on.

    $ SET NOON
    $ modem="TTA2:"
    $ cr[0,8]=13
    $ Retry: ON WARNING THEN GOTO Retry
    $ ALLOCATE 'modem'
    $ SET NOON
    $ SET TERMINAL/HOSTSYNC/TTSYNC/TYPEAHEAD/NOLOCAL/PASTHRU/NOECHO 'modem'
    $ SHOW TERM 'modem'
    $ INQUIRE ans "turn modem on and hit return"
    $ WRITE SYS$OUTPUT "Setting up modem""
    $ OPEN/READ/WRITE modem 'modem'
    $ CALL TellModem "atq0v1e1"
    	... other setups...
    $ CLOSE modem
    $ DEFINE/USER SYS$INPUT SYS$COMMAND
    $ SET HOST/DTE 'modem'
    	...
    $ EXIT
    $!
    $!
    $ TellModem: SUBROUTINE
    $ WRITE SYS$OUTPUT "Sending modem ''p1'"
    $ READ/TIME=1/ERR=noresp/PROMPT="''p1'''cr'" modem response
    $ SHOW SYMBOL response
    $ retry: READ/TIME=1/ERR=endresponse/PROMPT="" modem response
    $   SHOW SYMBOL response
    $   GOTO retry
    $ noresp:
    $ stat=$STATUS
    $ WRITE SYS$OUTPUT "No response, status=''stat'"
    $ endresponse: EXIT
    $ ENDSUBROUTINE