Communication software for concurrent real-time control

The authors describe simple effective communication software that provides a set of portable high-level primitives through which internal processes in any subsystem can interact in a uniform way, independently of the system configuration. Three forms of interprocess communications are provided: asynchronous send, in which the sending process does not wait; synchronous send, in which the process that sends a message is forced to wait until it is received by the destination process; and remote procedure call, in which a rendezvous between the caller and the acceptor takes place. The communication software is organized as a set of service processes that relies only on two low-level functions. The package has been made available on a number of different systems. Tests have been made on several network configurations. The organization of the communication software and the features that make it portable and suitable for real-time applications are described