C-TCP-Server

A simple TCP server implementation in C using the POSIX Socket API.

Overview

This project demonstrates the fundamentals of TCP server programming using POSIX sockets on Linux.

The application creates a TCP socket, binds it to a local IPv4 address and port, listens for incoming client connections, accepts a connection request, and receives a text message over a reliable TCP connection.

This project is designed for educational purposes and serves as a foundation for learning socket programming in C.

---

Project Structure

C_TCP_Server/
│
└── main.c

---

Technologies

C

• POSIX Sockets
• socket()
• bind()
• listen()
• accept()
• recv()
• sockaddr_in
• inet_addr()
• htons()
• close()

---

Communication

+----------------------+          TCP           +----------------------+
| TCP Client           | --------------------> | C TCP Server         |
| Any TCP Client       |                       | Linux / POSIX        |
+----------------------+                       +----------------------+

Default configuration:

Setting	Value
Protocol	TCP
IP Address	127.0.0.1
Port	2525

---

How It Works

1. Create a TCP socket.
2. Configure the server IPv4 address and port.
3. Bind the socket to the local address using bind().
4. Put the socket into listening mode using listen().
5. Wait for an incoming client connection using accept().
6. Receive a text message from the connected client using recv().
7. Close the client socket and the listening socket.

---

Connection Flow

socket()
    │
    ▼
bind()
    │
    ▼
listen()
    │
    ▼
accept()
    │
    ▼
recv()
    │
    ▼
close()

---

Learning Goals

This project demonstrates:

• Basic TCP socket programming
• TCP server implementation
• IPv4 networking
• Connection-oriented communication
• POSIX Socket API
• Receiving data over TCP
• Client connection handling
• Basic server workflow

---

Notes

• This project implements only the server side of a TCP connection.
• The server waits for a client to establish a connection before receiving data.
• The default configuration uses the loopback interface (127.0.0.1) for local testing.
• This example accepts a single client connection and receives a single message.
• The project focuses on understanding the fundamental TCP server workflow rather than building a production-ready server.

---

Future Improvements

• Send responses back to the client
• Bidirectional communication
• Support multiple clients
• Multi-threaded server
• IPv6 support
• Better error handling
• Binary data transfer

---

Related Projects

• Socket-Programming
• TCP Client (C++)
• UDP Example (C++ & C#)

---

What is POSIX?

POSIX (Portable Operating System Interface) is a family of IEEE standards that defines a common programming interface for Unix-like operating systems.

This project uses the POSIX Socket API, including functions such as:

• socket()
• bind()
• listen()
• accept()
• recv()
• close()

Because these APIs are standardized, the same networking code can typically be compiled and run on many Unix-like operating systems with little or no modification, including:

• Linux
• macOS
• FreeBSD
• OpenBSD
• NetBSD

---

Output:

---

Thanks

Mohammad Yousefi