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

144 Chapter7
Programming for PAD, DTC Telnet, Telnet/iX Server, and VT Devices
Telnet/iX Server Access on MPE/iX Systems
10, 12 Set parity type
11 Set parity generation and checking
26 Enable/disable XON/XOFF flow control
27 Set XOFF timer value
56 Specify data bits per character
64 Ignore parity error on input mode
72 Return PAD line speed
73 Set FCLOSE timeout value
74 Suppress the last form feed
FREAD and FWRITE
In general, the Telnet/iX Server will support the same size data buffers
for FREAD and FWRITE as the DTC. Currently, Telnet/iX 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, Telnet/iX 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 may support larger buffers. If an application
attempts to issue an FWRITE larger than the configuration
supports, the data will not be processed. 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.