Telnet/iX Server Access on MPE/iX Systems

For details on using the Telnet/iX Client and Server on MPE/iX systems, as well as information on the Telnet/iX Client commands, refer to the HP Telnet/iX User's Guide. For more information on configuring Telnet/iX, as well as more general information on Internet Services, please refer to Configuring and Managing MPE/iX Internet Services.

What's Included

This section includes information on:

Limits and restrictions that apply to Telnet/iX Server connected devices.
Recommended programming practices for Telnet/iX Server support.

General Telnet/iX Server Restrictions

Only sessions, not jobs, can be established on the MPE/iX system by the local Telnet client.
Although you may use the MPE/iX CONSOLE command to switch the console device to a previously connected Telnet/iX Server Ldev, [CTRL]-a and [CTRL]-b functionality are not supported on Telnet/iX Server Ldevs.
Use of customized terminal types is not supported.
Many FCONTROL and FDEVICECONTROL intrinsics, including all block modes, require the use of a 2392 compatible terminal emulator on the Telnet client side.

Telnet/iX Server Programming Considerations

The following provides details on the limitations of file system intrinsics used to control devices connected to an MPE/iX system via Telnet/iX. For more information about the following intrinsics, refer to Chapter 8 “Intrinsics Reference” of this manual.

FCONTROL

Some FCONTROLs are not supported for use with Telnet/iX Server connections. If a program uses an unsupported FCONTROL for a Telnet/iX connected device, the Telnet/iX driver will return a CCE condition code, but no device control action will take place. Any values returned in these calls may not be a true reflection of device control settings. These FCONTROLs include:

FCONTROL(10), set line speed.
FCONTROL(11), set line speed.
FCONTROL(22), return last read time.
FCONTROL(23), disable parity generation and checking.
FCONTROL(24), enable parity generation and checking.
FCONTROL(36), define parity setting.
FCONTROL(37), set terminal type and speed.
FCONTROL(38), set terminal type.
FCONTROL(40), determine current speed.

The following FCONTROLs are not supported when the local device is an HP-UX client:

FCONTROL(28), disable user block mode.
FCONTROL(29), enable user block mode.

Use of FCONTROL(27) (enable binary mode) when the local device is an HP-UX Telnet client, will require the user to set the HP-UX client into binary (using the HP-UX Telnet client toggle command) before the FCONTROL(27) is issued to the Telnet/iX Server. If the HP-UX client is not set into binary before the FCONTROL(27) is issued, the FCONTROL will return with CCL. The user must disable binary on the HP-UX client before binary is disabled on the Telnet/iX Server with FCONTROL(28).

Some caution should be taken when using FCONTROL(4), which sets a timeout interval for a read. Keep in mind that some delays may be caused by the network over which your Telnet connection is operating. In such cases you may want to add some time to the timeout value you would normally specify for the call.

FDEVICECONTROL

Some FDEVICECONTROLs are not supported for use with Telnet/iX Server connections. If a program uses an unsupported FDEVICECONTROL, the Telnet/iX driver will return a CCE condition code, but no device control action will take place. Any values returned in these calls may not be a true reflection of device The following discussion deals with parm1 values with 192 specified as controlcode.

Unsupported FDEVICECONTROLs include:

parm1: Action
1: Specify terminal type or printer type file
3: Set line speed
8: Return last input time
9, 11: Set parity generation and checking
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:

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.
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.

Telnet/iX Server Access on MPE/iX Systems

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