This is a project i developed for the Laboratory 2 course at university. The project consists of implementing multithreading and inter-process communication to optimize computations across multiple files.
The client uses multithreading to speed up data transmission. To simplify communication, the producer-consumer technique was adopted, where the main thread (masterworker) is the producer, and the threads (workers) are the consumers.
This system sends one file at a time to each thread, ensuring data insertion when slots are available through the use of data_items and free_slots semaphores. The pcmux mutex ensures that only one thread can access the data at a time, preventing undesirable overwrites by the masterworker or two workers reading the same file from the shared buffer pcbuff.
To check if the server is active, the application attempts to open and close a connection with the server three times at one-second intervals using the check_server() function. This prevents the program from closing if the server is active but temporarily unable to receive initialization through the network, helping determine if the server is indeed active.
To ensure the correct transmission of data and termination of the server, data is sent by the workers in the following format, with a 4-byte integer:
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If the integer is 0, it indicates the start of data exchange in the following format:
- Message length (4 bytes)
- Calculated sum (8 bytes)
- File name (message length - 8 bytes)
If the received length is negative, it indicates connection closure initiated by the thread.
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Otherwise, it will be interpreted as a server shutdown message.
This system distinguishes data exchange from other actions using the first 4 bytes, while a negative length signals the server threads to terminate or continue exchanging data among threads.
The server reads the first 4 bytes to determine if it’s a data exchange initiation or a shutdown message. If it's data exchange, the newly created connection is handed over to a thread that will receive data according to the format described above, allowing for faster handling of requests from multiple clients.
A dedicated thread was chosen to wait for the SIGINT signal. This thread shares a variable with the masterworker to signal when SIGINT arrives, instructing it to stop sending data to the buffer, terminate the threads, and send the shutdown message to the server.