MANAGER@SKIDMORE.BITNET.UUCP (09/17/87)
I've come upon a weird inconsistency in the Screen Management
routines (SMG$) that has me puzzled. Our users connect to the VAX
via two paths...
Most connect via a PBX at 9600 baud. The PBX provides
port selection.
Others connect via modem to the pbx at 1200 baud using
Hayes compatible modems. Since the modem lines connect
through the PBX, the VMS terminal characteristics are
identical for all VAX ports.
When I write Pascal programs employing the SMG$ run time library I
get different behavior in the following setting. If the screen contains
blank space, either because of a virtual display pasted at other than
column 1 or because of multiple spaces within a line, it is displayed
correctly on the pbx lines but incorrectly on the modem lines even though
the code is identical.
We have several programs that involve direct screen addressing (written
prior to SMG$). These behave consistently across communication lines.
Therefore, I doubt if the modems lose characters (besides which, the
inconsistencies always happen at the same screen locations).
My questions...
Has anyone else seen this problem or is it unique to our location?
Does SMG$ automatically change port characterstics?
Can you offer any other clues as to why SMG$ routines refuse to work
properly on modems?
PS. Our end devices are Rainbows, VT100's, and PRO350's -- all show
the same screen problems.
===================================================================
Leo D. Geoffrion BITNET: MANAGER@SKIDMORE.BITNET
Associate Director for NYNEX: (518) 584-5000 Ext. 2628
Academic Computing
Skidmore College
Saratoga Springs, NY 12866leichter@VENUS.YCC.YALE.EDU ("Jerry Leichter") (09/18/87)
...Our users connect to the VAX via two paths [via PBX at 9600 baud or via modem, throught the PBX, at 1200 baud]... When I write Pascal programs employing the SMG$ run time library I get different behavior in the following setting. If the screen contains blank space, either because of a virtual display pasted at other than column 1 or because of multiple spaces within a line, it is displayed correctly on the pbx lines but incorrectly on the modem lines even though the code is identical.... As far as VMS - and certainly SMG! - can tell, the ONLY difference between a dial-up line and a direct connection is the speed: Unless you have a very strange PBX, the lines as seen by the VAX ALWAYS have modem control. PBX's I know about provide no information to a host as to whether the "far side" of the link they are providing is comming from a dial-up line, a direct connection, or anything else (X.25, T1 mux, who knows what else). That being the case, you are going to have to look for some other distinction between your two situations. I can only guess, since in a rather long note you've provided little information as to what you actually SEE - "the output is 'wrong'": HOW? - as opposed to surmises about causes (SMG plays around with the modem) which cannot be relevent. So: There are three differences I can see between your two setups: a) The line speed; b) The presense of a modem in the data path; c) The actual particular terminals at the far end. It's very unlikely that (a) is relevent, but that's real easy to check: Just set one of your direct-connect lines to 1200 baud and see what you get. You can similarly check (c) by making sure that the devices are identical: Not just the same KIND of device, but all the same setup settings. Similarly, make sure that the VMS terminal settings are REALLY IDENTICAL in both cases. Two guesses: You are setting your lines up assuming an eight-bit data path and setting your modems to provide only a 7-bit path. (This would screw up a lot of things, but without knowing what kinds of things you've tried, I can't rule it out.) Since your problems show up with spacing, make sure that (a) Tab stops are set correctly on all devices - MUST be every 8 spaces; (b) the VMS SET TERM/TAB setting is the same for all lines involved. -- Jerry ------