feat(lab7): implement iterative TCP server/client with dual-protocol parsing and tmux automation

[Veexeq]

Description

This Pull Request introduces the complete implementation of Lab 7: Socket-based Inter-Process Communication. It delivers a robust, production-ready iterative TCP/IPv4 server capable of dual-protocol parsing (HTTP/1.1 and custom text commands), a dedicated network client utility, and a fully automated tmux integration testing harness.

The entire codebase is strictly compliant with the ISO C11 standard and enforces rigorous error policing (-Werror).

Technical Implementation Highlights

• Dual-Protocol State Machine: The server listens on port 9000 across all interfaces (INADDR_ANY). It dynamically differentiates between incoming HTTP GET/POST sequences (incrementing the session counter by 1 and responding with compliant HTTP/1.1 plain-text payloads) and custom ZADANIE <value> datagram streams (incrementing the counter by the arbitrary integer and returning raw payload text).
• Graceful Shutdown & Signal Hooking: Implemented a POSIX-compliant sigaction() interface to intercept SIGINT (Ctrl+C). It safely flips a volatile sig_atomic_t flag, enabling blocking system calls like accept4() to fail naturally with EINTR, breaking the main event loop, and executing clean descriptor deallocation.
• Resource Leak Prevention: Utilizes the modern Linux-specific accept4() system call decorated with the SOCK_CLOEXEC flag to prevent descriptor pollution across process boundaries.
• Network Resilience: Embedded the MSG_NOSIGNAL flag during standard send() routines to prevent the kernel from delivering a fatal SIGPIPE signal to the process if a client unexpectedly drops the connection.
• Structural Portability: Full compliance with Network Byte Order conventions using htons() and htonl() macro wrappers.

Directory Topology Added

.
├── Makefile
├── bin/
├── obj/
├── include/
├── scripts/
│   └── test_automation.sh
└── src/
    ├── client/
    │   └── main.c
    └── server/
        └── main.c

Verification & Testing Performed

1. Automated Integration Test Suite

Validated end-to-end communication via the custom scripts/test_automation.sh harness. The execution sequence spawns a standalone tmux session, synchronizes local execution directories, runs sequential programmatic client queries, captures state tracking output, and triggers a clean shutdown.

chmod +x scripts/test_automation.sh
./scripts/test_automation.sh

2. Manual Diagnostics

• Validated server compliance with local web browsers (HTTP GET /).
• Simulated raw interface manipulation via netcat: echo -n "ZADANIE 42" | nc 127.0.0.1 9000.
• Inspected network states using modern socket statistics utility: ss -tulpn.

3. Memory Profiling (Valgrind Audit)

Analyzed the executable layer via Valgrind Memcheck to verify strict memory management and prevent kernel object leaks.

valgrind --leak-check=full ./bin/server

Result: All heap blocks were freed -- no leaks are possible.