Asynchronous Serial Communications Programmer's Reference Manual (32022-90052)
148 Chapter7
Programming for PAD, DTC Telnet, Telnet/iX Server, and VT Devices
Virtual Terminal Access on MPE/iX Systems
FDEVICECONTROL(28)(block mode types supported) and
FDEVICECONTROL(62) (set quiesce I/O) are not supported for use
when the remote device is a PC or an HP-UX client.
FDEVICECONTROL(51) (set typeahead mode) is not supported on
MPE V remote devices or PCs without appropriate NS software.
Additionally, HP-UX (VT3K) supports single echo typeahead only.
FDEVICECONTROL(60) (flush typeahead buffer) and
FDEVICECONTROL(61) (bypass typeahead buffer) only support
MPE/iX remote devices or PCs with appropriate NS software.
The following FDEVICECONTROLs are supported with MPE/iX hosts
and PC clients running appropriate software only. These
FDEVICECONTROLs apply to functionality introduced in MPE/iX
release 4.5 and PC code NS 2.1 version B.03.00. The
FDEVICECONTROLs affected include:
• FDEVICECONTROL(63), set single echo typeahead mode.
• FDEVICECONTROL(65), set inter-byte timer.
• FDEVICECONTROL(66), define multiple type 2 EOR characters
(AEOR).
• FDEVICECONTROL(67), define delete (DEL) to backspace (BS)
mapping.
• FDEVICECONTROL(68), enable/disable escape sequence read
termination.
• FDEVICECONTROL(69), enable/disable suppress echo of read
termination characters.
FREAD and FWRITE
In general, VT will support the same size data buffers for FREAD and
FWRITE as the DTC. Currently, VT services will accept data buffers up
to 4096 bytes long. However, communicating with PC clients is limited
to buffers no larger than 3500 bytes. When communicating with a PC
client, VT will not support transfers larger than 3500 bytes. Data loss
may occur if you exceed the 3500 byte buffer limitation.
Recommended Programming Practices
Application developers are encouraged to use programming practices
that will facilitate successful operation in many different network
configurations.
The following should be considered:
1. Because the PC only supports a 3500 byte data buffer, applications
should only issue FREADs and FWRITEs of less than 3500 bytes
even though the DTC and other VT configurations may support
larger buffers. If an application attempts to issue an FWRITE larger