TCP Echo Server

              
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 12345
#define BUFFER_SIZE 1024

int main() {
    int server_fd, client_fd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(client_addr);
    char buffer[BUFFER_SIZE];
    ssize_t bytes_read;

    // Create a TCP socket
    server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // Set up the server address struct
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY; // Listen on any interface
    server_addr.sin_port = htons(PORT);

    // Bind the socket to the specified port and address
    if (bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }

    // Listen for incoming connections
    if (listen(server_fd, 1) < 0) {
        perror("listen failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }
    printf("Echo server listening on port %d...\n", PORT);

    // Accept a client connection
    client_fd = accept(server_fd, (struct sockaddr *)&client_addr, &addr_len);
    if (client_fd < 0) {
        perror("accept failed");
        close(server_fd);
        exit(EXIT_FAILURE);
    }
    printf("Client connected.\n");

    // Echo loop: receive data and send it back
    while ((bytes_read = recv(client_fd, buffer, BUFFER_SIZE, 0)) > 0) {
        // Send the received data back to the client
        send(client_fd, buffer, bytes_read, 0);
    }

    printf("Client disconnected.\n");
    close(client_fd);
    close(server_fd);
    return 0;
}