NIO CommKit Host Interface Installation and System Administration Manual

6-7

Porting CommKit Applications To Release 4.x

Programmer-Level Compatibility

The architectural changes of this release of the CommKit software impact all

applications that access the library and system call interface.

In particular, this release of the CommKit software does not support an ioctl

interface. All ioctl calls are reserved for use by the interface library and their

calling sequences are not guaranteed.

Porting old applications to the new release will, however, yield simpler,

more robust code. The sections that follow discuss the changes and show

examples of the new library routines and system calls. Many of the

examples are taken from the CommKit user-level commands.

STREAMS

You should be familiar with the characteristics of STREAMS I/O and the

information in STREAMS/UX for the HP 9000 Reference Manual. In

general, you do not need to change applications that use the standard I/O

library function calls, except to account for STREAMS errors.

One aspect of STREAMS that you should be aware of is the handoff nature

and internal buffering of writing data. A write system call to a stream will

return immediately from the stream head and the data will be queued to the

downstream modules and drivers. If the network is very busy or the driver

cannot transmit the data, the stream will eventually exert ﬂow control, but

only after multiple write system calls complete. For more information, refer

to the section describing write(2) later in this chapter.

TTY Interface

This release of the CommKit software, unlike previous releases, does not

reimplement the HP-UX TTY interface. Instead, it uses the standard TTY

STREAMS modules, ldterm and ptem.