The idea is to use low level C libraries to implement user level threads, semaphores and message passing between these threads. Then a client server application is created using our own threads, semaphores and message passing system.

• Using functions from ucontext.h we created a simple user level thread library (a tiny version of POSIX threads) in C
• Check thread.h for details
• Using these threads, we implemented wait() and signal() functions for semaphores
• Check Sem.h for details
• To check correctness of the sempahore library created above, we implemented the classic readers-writers problem
• Using the semaphore library created above, we implemented a single machine message passing system among threads we created above. The idea is to build ports which threads use to send and receive messages from. Each port is a buffer and controlled using semaphores like a producer consumer problem. As this is a single machine implementation, we have shared memory. You can think of it like message passing between processes on a single machine. These processes share memory at kernel level, we mimiced the same at user level among threads
• Check msgs.h for details
• To check the correctness of the message passing system we built above, we implemented a server-client model with 3 clients and one server
• Check cl-srv.c for implementation details

Requires linux OS to run

gcc tcb.h && gcc q.h && gcc thread.h && gcc Sem.h && gcc && ./a.out