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LAT Programming via $qio?

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The Question is:

Section of the I/O Users guide deals with Programming [LAT] Application
 Ports. It describes a return status of TIMEOUT but its not clear how to
 request a connection with a timeout. What I'm trying to do is write a C
 program that "opens" a LT devic
e which has been set up as an Application mode port in LATCP. I'm interested
 both in waiting for a period of time, waiting "forever" and "complete it ifs
 available, fail if it isn't".
Also I've experimented a bit with this and I've found some strange results. If
 I look at the port in LATCP I see its marked as "queued". However if on a
 single node one process has it open, a 2nd process will get a
 SYSTEM-F-DEVACTIVE error. I thought that
 since its marked as a queued port the 2nd process should get suspended until
 it cancels the request or the port becomes available.
The other strange thing I've seen is that if I have the printer open by a
 process on one node and I try to open it from a process on a different node
 (node B) the process on node B will hang, waiting for it. The strange part is
 that if a 2nd process on no
de B comes along and tries to open the device (while the 1st process on node B
 is still hanging) then the 2nd process gets a SYSTEM-F-DEVACTIVE as described
 above but then the 1st process on node B gets SYSTEM-F-ABORT, iosb+2 = 12
 (Entry is not in queue).
If it matters the DECServer the printer is attached to is a DS700 and queuing
 is not enabled on the port (on the DECserver side).

The Answer is :

  You can quite easily establish your own timeout using
  standard OpenVMS system services.
  LAT is an asymmetric protocol.  The queued setting applies
  to the remote (receiving) end of the connection -- in the cited
  case, the port the printer is connected to should be marked as
  queued.   (Remember that OpenVMS is generally a client of the
  terminal server, unless you are using reverse LAT and connecting
  out from OpenVMS to the terminal server.  Also please see the
  documentation section detailing on a forward port.)
  Without an example of the particular applications, a more
  specific answer is difficult -- please contact the Compaq
  Customer Support Center for assistance and examples.

answer written or last revised on ( 28-APR-2000 )

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