Both technical and commercial applications are increasingly being implemented as distributed systems running in a network of workstations. In this paper we describe an object-oriented class library for UNIX interprocess communication. We concentrate on applying object-oriented design techniques for the architecture of the library, which results in greater flexibility and easier extensibility. The library supports the construction of hybrid systems, as both sending objects and conventional data structures is possible. Thus it allows the easy integration of object-oriented and conventional systems, facilitating migration strategies towards object-oriented programming. The library already proved its value in a large industrial project for a process control system in a steel plant.