#include        <sys/types.h>   /* basic system data types */
#include        <sys/socket.h>  /* basic socket definitions */
#include        <netinet/in.h>
#include        <stdio.h>
#include        <unistd.h>
#include	<strings.h>

#define MAXLINE 1024

void
dg_echo(int sockfd, struct sockaddr *pcliaddr, int clilen)
{
  int n;
  int len;
  char mesg[MAXLINE];

  for ( ; ; ) {
    len = clilen;
    n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);
    
    sendto(sockfd, mesg, n, 0, pcliaddr, len);
  }
}

int
main(int argc, char **argv)
{
  int sockfd;
  struct sockaddr_in servaddr, cliaddr;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  
  bzero(&servaddr, sizeof(servaddr));
  servaddr.sin_family      = AF_INET;
  servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
  servaddr.sin_port        = htons(6789);
  
  bind(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
  
  dg_echo(sockfd, (struct sockaddr *) &cliaddr, sizeof(cliaddr));

  return 0;
}