#include netinetinh#include netinetiph#include stdioh#include stdlibh#include stringh#include syssocketh#include unistdh#define ECHO_PORT 9999#define BUF_SIZE 4096int close_socketint sock if closes

This is a simple echo server program written in C. The server listens on the specified port and waits for incoming connections. When a connection is established, the server reads data from the client and sends it back to the client. The program uses socket programming to create and manage sockets.

The program first creates a socket using the socket() function, and then binds it to a specified port using the bind() function. It then listens for incoming connections using the listen() function.

When a client connects, the program accepts the connection using the accept() function. It then reads data from the client using the recv() function, and sends it back to the client using the send() function. This loop continues until the client closes the connection or an error occurs.

If an error occurs during any of these steps, the program prints an error message and terminates with a failure status. If everything works correctly, the program terminates with a success status.

Overall, this program demonstrates the basics of socket programming and how to create a simple server that can communicate with multiple clients