TCP server with non blocking socket.

tcp_server_non_blocking.c

#include <stdio.h>                                                                                                                                                      
#include <stdlib.h>                                                                                                                                                     
#include <stdlib.h>                                                                                                                                                     
#include <string.h>                                                                                                                                                     
#include <unistd.h>                                                                                                                                                     
#include <errno.h>                                                                                                                                                      
                                                                                                                                                                        
#include <netdb.h>                                                                                                                                                      
#include <sys/types.h>                                                                                                                                                  
#include <sys/socket.h>                                                                                                                                                 
#include <arpa/inet.h>                                                                                                                                                  
#include <netinet/in.h>                                                                                                                                                 
#include <sys/wait.h>                                                                                                                                                   
#include <fcntl.h>                                                                                                                                                      
                                                                                                                                                                        
                                                                                                                                                                        
#define PORT "8000"
#define HOST "127.0.0.1"
#define MAX_LISTEN 5


void *get_in_addr(struct sockaddr *sa){
    if(sa->sa_family == AF_INET){
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void){

    int sd, new_sd;
    int yes = 1;
    int rv;
    char s[INET6_ADDRSTRLEN];

    struct addrinfo hints, *serverinfo, *p;
    struct sockaddr_storage their_addr; // COnnectors address info.
    socklen_t sin_size;

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;

    if((rv = getaddrinfo(NULL, PORT, &hints, &serverinfo)) != 0){
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // Loop through different results and pick up the first one.
    for( p = serverinfo; p != NULL; p = p->ai_next){

        if ((sd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
            perror("server: socket");
            continue;
        }

        if((fcntl(sd, F_SETFL, O_NONBLOCK)) < 0){
            perror("error:fnctl");
            exit(EXIT_FAILURE);
        }

        if(setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &yes,
                    sizeof(int)) == -1){
            perror("setsockopt");
            exit(1);
        }

        if(bind(sd, p->ai_addr, p->ai_addrlen) == -1){
            close(sd);
            perror("server: bind");
            continue;
        }

        break;
    }

    if (p == NULL){
        fprintf(stderr, "server: failed to bind \n");
        return 2;
    }

    freeaddrinfo(serverinfo); // No need for it further.


    if(listen(sd, MAX_LISTEN) == -1){
        perror("listen");
        exit(1);
    }


    printf("server: waiting for connections...\n");

    while(1){
        sin_size = sizeof their_addr;
        new_sd  = accept(sd, (struct sockaddr *)&their_addr, &sin_size);

        if(new_sd == -1){
            perror("accept ...");
            sleep(1);
            continue;
        }

        inet_ntop(their_addr.ss_family,
                get_in_addr((struct sockaddr *)&their_addr),
                s, sizeof s);

        printf("server: got connection from %s \n", s);

        if(!fork()){ // This is child process.
            close(sd); // Child doesn't need the listner socket. I'm not sure thought.
            while(1){
                int sent = send(new_sd, "Hello...", 8, 0);
                if(sent == -1)
                    perror("send");
                else
                    printf("Send packet");
            }
            close(new_sd);
            exit(0);
        }
        close(new_sd); // Parent doesn't need child's socket.
    }

    return 0;
}