Open System Services Programmer's Guide

1
Applies to both AF_UNIX Release 2 sockets and earlier AF_UNIX sockets. However, AF_UNIX Release 2 sockets must
be of the same mode to communicate with each other. See “Using AF_UNIX Sockets” (page 187).
Table 19 lists the interprocess-communication methods available to an OSS process using mixed
OSS and Guardian APIs, and the capabilities of each relevant to communication between processors
and nodes. The methods are listed in an order consistent with Table 18.
Table 19 Interprocess Communication Using OSS and Guardian APIs
With other systemsBetween Expand
nodes
Between processorsWithin a processorIPC method
YesYesYesYesGuardian AF_INET
and AF_INET6
sockets
YesYesYesYesOSS AF_INET and
AF_INET6 sockets
NoNoYesYesOSS AF_UNIX
sockets
1
NoNoYesYesPipes (with OSS
processes only)
NoYesYesYesFIFOs
NoNoYesYesMessage queues (with
OSS processes only)
NoNoYesYesOSS signals
NoNoNoYesShared memory
2
NoNoNoYesGuardian binary
semaphores
NoNoNoYesOSS semaphores (with
OSS processes only)
NoYesYesYes$RECEIVE
1
Applies to both AF_UNIX Release 2 sockets and earlier AF_UNIX sockets. However, AF_UNIX Release 2 sockets must
be of the same mode to communicate with each other. See “Using AF_UNIX Sockets” (page 187).
2
On servers running J06.12 or later J-series RVUs or H06.23 or later H-series RVUs, Guardian processes can use OSS
function calls to access shared memory. See “Using Shared Memory” (page 189) for more information.
Common and Unique Characteristics
OSS interprocess communication includes most UNIX interprocess-communication methods. The
extensions and differences of OSS interprocess-communication functions compared to typical UNIX
interprocess communication are summarized in Table 20 (page 197). Table 22 (page 204) summarizes
the behavior of Guardian interprocess-communication procedures when called from OSS processes.
Features Common to UNIX and OSS Interprocess Communication
Sockets are the most widely used API for communication between processes running on different
systems. The semantics used by sockets applications vary from UNIX system to UNIX system.
OSS sockets are based on the versions of UNIX systems developed at the University of California,
Berkeley, by the Berkeley Software Distribution (BSD) group. The OSS implementations (BSD 4.3
for AF_INET and AF_INET6, and BSD 4.3+ for AF_UNIX) have limited extensions based on the
XPG4 standard. OSS sockets obey semantics consistent with the POSIX.1G draft standard.
For a good introduction to the use of sockets, refer to a commercial text such as UNIX Network
Programming, Second Edition, by W. Richard Stevens.
Common and Unique Characteristics 175