Open System Services Porting Guide (G06.29+, H06.06+, J06.03+)

The poll() Function
On a UNIX system, the poll() function provides applications with a mechanism for multiplexing
input and output (blocking I/O) over a set of file descriptors. It identifies those file descriptors on
which an application can read or write data, or on which certain events have occurred. poll()
supports regular files, terminal devices, sockets, STREAMS-based files, FIFOs, and pipes.
If your program calls poll(), you must use the select() function or the Guardian
FILE_COMPLETE_ procedure call instead. The select() function supports only OSS file descriptors,
while the FILE_COMPLETE_ procedure supports both OSS file descriptors and Guardian file numbers.
For more information on the select() function, refer to the select(2) reference page either
online or in the Open System Services System Calls Reference Manual; for more information on
the FILE_COMPLETE_ procedure, refer to the Guardian Procedure Calls Reference Manual.
TLI/XTI
The Transport Layer Interface (TLI), as defined in UNIX System V Release 4 (SVR4), is a transport
independent interface that supports many transport interfaces, such as TCP/IP, OSI TP4, IPX/SPX,
and others. X/Open specifies XTI, with some minor enhancements; XTI is a superset of TLI. Both
interfaces are similar to the ISO transport service definition and provide functions similar to those
provided by sockets.
Open System Services does not support TLI or XTI. You must use an alternative approach: for
example, rewriting some parts of your code to use Guardian sockets. The steps used by a sockets
interface when listening for incoming calls and establishing transactions are very similar to TLI or
XTI, but the routines use different semantics. Thus, it is not difficult to modify a program that uses
TLI/XTI to use a Guardian sockets interface instead.
Using Interprocess Communication (IPC) Mechanisms
Most versions of UNIX possess many IPC mechanisms. When porting code to the OSS environment,
there is not always a complete correspondence of these IPC mechanisms and other features.
Table 6 (page 88) lists the IPC methods available in Open System Services using only the OSS
APIs and the capabilities of each API relevant to communication between processors and nodes.
Table 6 Interprocess Communication Using OSS APIs
With other systemsBetween Expand
nodes
Between processorsWithin a processorIPC method
YesYesYesYesOSS AF_INET and
AF_INET6 sockets
NoNoYesYesOSS AF_UNIX
sockets
1
NoNoYesYesPipes
NoYesYesYesFIFOs
NoNoYesYesMessage queues
NoNoYesYesOSS signals
NoNoNoYesShared memory
NoNoNoYesOSS semaphores
NoYesYesYes$RECEIVE
88 OSS Porting Considerations