Open System Services Programmer's Guide

6 Interprocess Communication
Interprocess-communication mechanisms allow processes to communicate within the same processor,
between processors, and between nodes. This section discusses the following topics:
ContentTopic
Summary of the mechanisms available to an OSS
application.
“Available Methods” (page 174)
Summary of the differences between UNIX and OSS
interprocess communication.
“Common and Unique Characteristics” (page 175)
Summary of OSS and Guardian processes ability to
communicate using OSS and Guardian
interprocess-communication methods
“Interprocess-Communication Interoperability” (page 176)
Suggestions regarding the use of
interprocess-communication mechanisms to improve
application performance.
“Performance Considerations” (page 195)
List of each OSS interprocess-communication function with
notes about its OSS implementation and its use when called
from Guardian processes.
“OSS Interprocess-Communication Functions” (page 196)
List of each Guardian interprocess-communication
procedure with notes about its use when called from OSS
processes.
“Guardian Interprocess-Communication Procedures”
(page 203)
Available Methods
The OSS application program interface (API) provides access to the sockets, pipes, FIFOs, shared
memory, semaphores, and message queues found on most UNIX systems. An OSS application
also has access to Guardian APIs that provide additional interprocess-communication methods
such as Guardian sockets and the Guardian requester/server interface known as the $RECEIVE
file. Some of the OSS and Guardian interprocess communication methods also allow OSS processes
to communicate with Guardian processes.
Table 18 (page 174) lists the interprocess-communication methods available in Open System Services
using only OSS APIs, and the capabilities of each relevant to communication between processors
and nodes. The methods are listed in approximate decreasing order of usage on UNIX systems.
Table 18 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
174 Interprocess Communication