#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h> //addrinfo
#include <stdio.h>

/*SYNTAX   ./serverUDPs */

char PORT[] = "47200";

int main(void) {
    char buf[50];
    int s, n;
    struct addrinfo hints, *result, *tmp;

    memset(&hints, 0, sizeof(hints)); /*It is important reset all to NULL*/

    hints.ai_family = AF_INET; //IPv4
    hints.ai_socktype = SOCK_DGRAM; //UDP
    hints.ai_flags = AI_PASSIVE; //Use the wildcard address

    if ((getaddrinfo(NULL, PORT, &hints, &result)) != 0) /*Checking status of getaddrinfo result*/
    {
        fprintf(stderr, "getaddrinfo error\n");
        exit(EXIT_FAILURE);
    }

    /* getaddrinfo() returns a list of address structures.
    Try each address until we successfully bind.
    If socket (or bind) fails, we (close the socket
    and) try the next address. */

    for (tmp = result; tmp != NULL; tmp = tmp -> ai_next)
    {
        s = socket(tmp->ai_family, tmp->ai_socktype, tmp->ai_protocol);
        if (s == -1)
        {
            continue;
        }
        if (bind(s, tmp -> ai_addr, tmp -> ai_addrlen) == 0)
        {
            break; //Success
        }
        close(s);        
    }
    
    freeaddrinfo(result); //No longer needed

    if (tmp == NULL)
    {
        fprintf(stderr, "Could not bind\n");
        exit(EXIT_FAILURE);
    }

    /* Read from the socket until end-of-file and
     * print what we get on the standard output.
     * "We receive mail, open it, and show it to everyone" */

    while ((n = recv(s, buf, sizeof(buf), 0)) > 0)
        write(1, buf, n);

    close(s);
    exit(0);
}