Channel (programming)

In computing, a channel is a model for interprocess communication and synchronization via message passing. A message may be sent over a channel, and another process or thread is able to receive messages sent over a channel it has a reference to, as a stream. Different implementations of channels may be buffered or not, and either synchronous or asynchronous.

Channels are fundamental to the process calculus approach to concurrency, and originated in communicating sequential processes (CSP), a formal model for concurrency, and has been used in many derived languages, such as occam, and Limbo programming language (via Newsqueak and the Alef programming language). They are also used in the C programming language threading library libthread, and in Plan 9 from Bell Labs, which uses libthread, as well as in Stackless Python and the Go programming language.

Channels modeled after the CSP model are inherently synchronous: a process waiting to receive an object from a channel will block until the object is sent. This is also called rendezvous behaviour. Typical supported operations are presented below using the example of the libthread channel API.

The Multithreading library, libthread, which was first created for the operating system Plan 9, offers inter-thread communication based on fixed-size channels.

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