Abstract
This paper presents a client-server debugging model, describes the design and implementation of a portable, scalable, practical distributed debugger based on this model, and compares it with the related work. The distributed debugger based on the sequential debugger gdb or dbx can efficiently support debugging various PVM and MPI programs, and its interfaces are implemented by Java. Therefore, it meets High Performance Debugging Standard's three general goals concerning parallel and distributed debuggers. In addition, it is portable, easy to learn and easy to use.