EMUNET: a debugging aid for distributed programs in TCP/IP based network

Most programmers depend on reproducible behavior of a program to locate its bugs. In a sequential program, the execution of the program can easily be repeated to find the bugs. When a program is distributed across network, the execution order of the program components varies from one run to another. It is very difficult, often impossible, to repeat the same sequence of execution, which makes debugging a program very difficult. This paper describes EMUNET, a tool that can aid debugging in distributed programming. Using EMUNET, the network functions in a distributed program are replaced with the software modules that communicate through memory. The distributed program then becomes a single process with multiple, user-controlled threads of execution. The programmer can compile and debug the distributed program as a single program. The behavior of the program is repeatable. Most of the bugs can be found in this way. When this initial debugging process is finished, the programmer can then link the distributed program with actual network library for real execution. No internal program changes are required.