Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)

Chapter 7 149
Programming for PAD, DTC Telnet, Telnet/iX Server, and VT Devices
Virtual Terminal Access on MPE/iX Systems
than the configuration supports, the data will not be processed. If
the remote host detects a buffer size support issue on the local client,
it will return a file system error FSERR32 to the application.
However, in the case of data transfer between remote host and PC
via a third system, the remote host will not detect the buffer size
support issue; the application thus receives no error although the
data is not processed.
2. Application programs should check for device availability after IO
requests. If a terminal logical device becomes unavailable, the
application will receive a file system error FSERR24 indicating that
the device is no longer available and that the application should
terminate. This guideline minimizes unnecessary use of CPU
resources.
3. Use FCONTROL rather than FDEVICECONTROL whenever
possible. Since not all FDEVICECONTROLs are supported on
MPE V systems, an FDEVICECONTROL may not work properly.
4. Use FFILEINFO with
itemnum value 60 and FCONTROL(39) if you
need to determine the network configuration. FFILEINFO with
itemnum value 60 will return an item value corresponding to the
terminal type of the device being accessed.
The item values returned from FFILEINFO are of the immediate
device. For example, a network configuration involving a PAD
connection to an HP 3000 and then a remote VT connection to another
HP 3000 will return an
item value 5 (NS Virtual Terminal).
FCONTROL(39) will return the terminal type value 24 corresponding
to the PAD device.