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

int main(int argc, char *argv[]) { 
    int sockid, buflen;
    struct sockaddr_in servsock, fromsock;
    size_t fromlen;
    char buf[30000], response[20];

    sockid = socket(PF_INET,  SOCK_DGRAM, IPPROTO_UDP);
    servsock.sin_family=AF_INET;
    servsock.sin_port=htons(53413);
    servsock.sin_addr.s_addr = htonl(INADDR_ANY);

    fcntl(sockid, F_SETFL, O_NONBLOCK);

    if (bind(sockid, (struct sockaddr *) &servsock, sizeof(servsock)) < 0) {
	printf("Cannot bind to port 53413\n");
    }

    bzero(buf, 30000);

    fromlen = sizeof(fromsock);
    while (1) { 
        if (recvfrom(sockid, buf, 30000, 0, 
                     (struct sockaddr *) &fromsock, &fromlen) > 0) {
            printf("foo sent %s. What do you want to reply?\n", buf);
            scanf("%s", &response);

            fromlen=sizeof(fromsock);
            if (sendto(sockid, response, strlen(response), 0, 
                   (struct sockaddr *) &fromsock, fromlen) < 0) {
              printf("sendto error\n");

            }
        }
    }
    
}