Most developers spend their time building APIs, dashboards, and CRUD systems. But at some point, I wanted to go deeper — to understand how servers actually work at a lower level. So I built a simple non-blocking multithreaded TCP server in C++. Why this project? This wasn’t about building something production-ready. It was about learning: How TCP servers handle multiple clients What “non-blocking I/O” really means in practice How multithreading impacts performance and scalability The hidden complexity behind backend systems Core Concepts 1. TCP Sockets The foundation of communication between client and server. Using low-level socket APIs gives full control — and full responsibility. 2. Non-Blocking I/O Instead of waiting for operations to complete, the server continues execution. This avoids: Blocking the entire process Wasting CPU cycles on idle connections 3. Multithreading Each connection can be handled independently, allowing multiple clients to interact with the server simultaneously. But this introduces new challenges: Thread management Synchronization issues Resource contention Key Challenges While building this, I ran into several real-world problems: Creating too many threads can kill performance Poor synchronization leads to race conditions Mixing non-blocking I/O with threads requires careful design This is where you start understanding why modern systems use: Thread pools Event loops (like epoll) Hybrid architectures What I Learned This project changed how I see backend systems. Things that look “simple” at a high level — like handling requests — are actually complex under the hood. You start to appreciate: Node.js event loop Nginx architecture High-performance networking systems What’s Next? I’m planning to evolve this project into something more advanced: Replace thread-per-connection with a thread pool Introduce event-driven I/O (epoll) Build a custom protocol on top of it Benchmark performance under load Source Code Check out the project here: https://github.com/HenriquesOmbisa/mojo-raw-cpp Final Thoughts If you’re a developer and you’ve never built something like this, I highly recommend it. It forces you to think differently. It pushes you beyond frameworks. And it gives you a real understanding of how systems work. This is where software engineering actually begins.