Creating Service Interfaces

One benefit of STREAMS is that it simplifies the creation of modules that present a service interface to any neighboring application program, module, or device driver. A service interface is defined at the boundary between two neighbors.

In STREAMS, a service interface is a specified set of messages and the rules for allowable sequences of these messages across the boundary. A module that implements a service interface will receive a message from a neighbor and respond with an appropriate action (for example, send back a request to retransmit) based on the specific message received and the preceding sequence of messages.

STREAMS provides features that make it easier to design various application processes and modules to common service interfaces. If these modules are written to comply with industry-standard service interfaces, they are called protocol modules.

In general, any two modules can be connected anywhere in a stream. However, rational sequences are generally constructed by connecting modules with compatible protocol service interfaces.