TCP listening non-blocking socket server template.

tcpserver.c

#include <sys/socket.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <netdb.h>
#include <netinet/in.h> 

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

#include <time.h>

#define PORT 8080

#define BUFF_SIZE 4096

#define SOCK_ADDR struct sockaddr

int main(int argc, char **argv){
    clock_t start, end;
    int sockfd, n,errcode,new_socket,opt=1; 
    int sendbytes;
    struct sockaddr_in servaddr;
    struct sockaddr_in destaddr;

    char sendline[BUFF_SIZE];
    char readline[BUFF_SIZE];

    // usage check 
    // if(argc != 2) 
    //     return 0; 

    sockfd = socket(AF_INET,SOCK_STREAM,0);

    // socket preparation

    bzero(&servaddr,sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = INADDR_ANY; 

    if(0 > (errcode = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR , 
                                                  &opt, sizeof(opt)))){
        perror("setsockopt");
        exit(EXIT_FAILURE);  // 0 - success, -1 - fail
    }

    if(0 > (errcode = bind(sockfd,&servaddr,sizeof(servaddr)))){
        perror("bind");
        exit(EXIT_FAILURE); 
    }
    
    if(0 > (errcode = listen(sockfd,4))){
        perror("listen");
        exit(EXIT_FAILURE); 
    }

    socklen_t cli_addr_size = sizeof(servaddr);
    if (0 > (new_socket = accept(sockfd, &destaddr,&cli_addr_size))) 
    { 
        printf("new_socket: %d",new_socket);
        perror("accept"); 
        exit(EXIT_FAILURE); 
    } 
    printf("Connection from: %s \n",inet_ntoa(destaddr.sin_addr));
    
    int flags = fcntl(sockfd,F_GETFL,0);
    if(0 > (flags)){
        perror("flags");
        exit(EXIT_FAILURE);  // 0 - success, -1 - fail
    }
    // assert(flags != -1);
    fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);

    while(new_socket > 0){

        n = read(new_socket , readline, BUFF_SIZE); 
        printf("%s\n",readline); 
        close(new_socket);
        new_socket = accept(sockfd, &destaddr,&cli_addr_size);

    }
    printf("Connection closed: %s \n",inet_ntoa(destaddr.sin_addr));
    
    return 0; 
}