Inter-process communication

For other uses, see IPC.

In computing, 'Inter-process communication' (IPC) is a set of techniques for the exchange of data among multiple threads in one or more processes. Processes may be running on one or more computers connected by a network. IPC techniques are divided into methods for message passing, synchronization, shared memory, and remote procedure calls (RPC). The method of IPC used may vary based on the bandwidth and latency of communication between the threads, and the type of data being communicated.

There are several reasons for providing an environment that allows process cooperation:

• Information sharing
• speedup;
• Modularity;
• Convenience; and
• Privilege separation.

IPC may also be referred to as inter-thread communication and inter-application communication.

The combination of IPC with the address space concept is the foundation for address space independence/isolation.^[1]

Main IPC Methods

Method	Provided by (Operating systems or other environments)
File	Most operating systems.
Signal	Most operating systems; some systems, such as Windows, only implement signals in the C run-time library and do not actually provide support for their use as an IPC technique.
Socket	Most operating systems.
Message queue	Most operating systems.
Pipe	All POSIX systems, Windows.
Named pipe	All POSIX systems, Windows.
Semaphore	All POSIX systems, Windows.
Shared memory	All POSIX systems, Windows.
Message passing (shared nothing)	Used in MPI paradigm, Java RMI, CORBA, MSMQ, MailSlots and others.
Memory-mapped file	All POSIX systems, Windows. This technique may carry race condition risk if a temporary file is used.

Implementations

There are a number of APIs which may be used for IPC. A number of platform independent APIs include the following:

• Anonymous pipes and named pipes
• Common Object Request Broker Architecture (CORBA)
• Freedesktop.org's D-Bus
• Distributed Computing Environment (DCE)
• Message Bus (MBUS) (specified in RFC 3259)
• MCAPI Multicore Communications API
• Lightweight Communications and Marshalling (LCM)
• ONC RPC
• Unix domain sockets
• XML XML-RPC or SOAP
• JSON JSON-RPC
• Thrift
• TIPC
• ZeroC's Internet Communications Engine (ICE)

The following are platform or programming language specific APIs:

• Apple Computer's Apple events (previously known as Interapplication Communications (IAC)).
• Enea's LINX for Linux (open source) and various DSP and general purpose processors under OSE
• IPC implementation from CMU.
• Java's Remote Method Invocation (RMI)
• KDE's Desktop Communications Protocol (DCOP)
• Libt2n for C++ under Linux only, handles complex objects and exceptions
• The Mach kernel's Mach Ports
• Microsoft's ActiveX, Component Object Model (COM), Microsoft Transaction Server (COM+), Distributed Component Object Model (DCOM), Dynamic Data Exchange (DDE), Object Linking and Embedding (OLE), anonymous pipes, named pipes, Local Procedure Call, Message loop, MSRPC, .NET Remoting, and Windows Communication Foundation (WCF)
• Novell's SPX
• POSIX mmap, message queues, semaphores, and Shared memory
• RISC OS's messages
• Solaris's Doors
• System V's message queues, semaphores, and shared memory
• Distributed Ruby
• DIPC Distributed Inter-Process Communication
• OpenBinder Open Binder
• IPC Shared Memory Messaging from Solace Systems

See also

• Computer network programming
• Communicating Sequential Processes (CSP paradigm)
• .NET Remoting
• Microkernel
• Nanokernel
• Protected procedure call

References

External links

• Linux ipc(5) man page describing System V IPC
• Windows IPC
• Beej's Guide to Unix IPC