echo_to_client.c

#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>

#define PORT 35000
#define BUF_SIZE 1024

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int addrlen = sizeof(address);
    char buffer[BUF_SIZE] = {0};
    
    // Creating socket file descriptor
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        return -1;
    }
    
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);

    int opt = 1;
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        perror("setsockopt");
        return -1;
    }

    
    // Bind the socket to the port 35000
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address))<0) {
        perror("bind failed");
        return -1;
    }
    while (1)
    {
        if (listen(server_fd, 3) < 0) {
            perror("listen");
            return -1;
        }
        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen))<0) {
            perror("accept");
            return -1;
        }
        // try to read the message from the client
        // if no message is received for 1 seconds, the connection is closed
        struct timeval tv;
        tv.tv_sec = 1;
        tv.tv_usec = 0;
        setsockopt(new_socket, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);
        int bytes_read = read(new_socket, buffer, BUF_SIZE);
        if (bytes_read > 0) {
            send(new_socket, buffer, bytes_read, 0);
        }
        close(new_socket);
    }
    return 0;
}