#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<netdb.h>
#include<fcntl.h>
#include<strings.h>

#define DNSPORT 53

void gensndbuff(unsigned char *sndbuff,int *blen,
		char * dname0, short id)
{
  short nid;  int i, j, k;  char dname[128];  int seglen;
  char seg[64];
  char cc;
  sprintf(dname,"%s.",dname0);  // copy to dname with extra .
  i = 0;
  nid = htons(id);
  sndbuff[i++] = *((char *)(&nid));
  sndbuff[i++] = *(((char *)(&nid)) + 1);
  sndbuff[i++] = 0x01;  sndbuff[i++] = 0x00;
  sndbuff[i++] = 0;  sndbuff[i++] = 1;  // QDCOUNT
  sndbuff[i++] = 0;  sndbuff[i++] = 0;  // ANCOUNT
  sndbuff[i++] = 0;  sndbuff[i++] = 0;  // NSCOUNT
  sndbuff[i++] = 0;  sndbuff[i++] = 0;  // ARCOUNT

  // question
  j = 0;
  while (j<strlen(dname))
    { seglen = 0;  cc = 0;
      while (cc != '.')
	{ cc = dname[j+seglen];
	  seg[seglen] = cc;  seglen++;
	} // inner while
      seg[seglen-1] = 0;  // 0-terminate string
      j = j + seglen;
      sndbuff[i++] = (unsigned char) (strlen(seg));
      for(k=0;k<strlen(seg);k++) sndbuff[i++] = seg[k];
    }  // while
  sndbuff[i++] = 0;  
  sndbuff[i++] = 0;  sndbuff[i++] = 1;  // QTYPE
  sndbuff[i++] = 0;  sndbuff[i++] = 1;  // QCLASS
  
  *blen = i;
} // gensndbuff

int main(int argc, char** argv) // ip of server, domain name
{
  int i, sockfd, x, y,result, plen, mlen, blen;
  unsigned char sndbuff[512];   // send buffer
  unsigned char rcvbuff[512];  // receive buffer
  struct sockaddr_in serveraddr;  // used by sendto

  sockfd = socket(AF_INET,SOCK_DGRAM,0);

  serveraddr.sin_family = AF_INET;
  serveraddr.sin_addr.s_addr = inet_addr(argv[1]);
  serveraddr.sin_port = htons(DNSPORT);
  plen = sizeof(serveraddr);  

  gensndbuff(sndbuff,&blen,argv[2],5);
  sendto(sockfd,sndbuff,blen,0,
	 (struct sockaddr*)&serveraddr,plen);
  
  result = recvfrom(sockfd,rcvbuff,512,0,NULL,NULL);

  printf("Response from server: \n");
  for(i=0;i<result;i++) printf("%d ",rcvbuff[i]);
  
  close(sockfd);
  exit(0);
}