/* Datagram client in the internet domain */
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<netdb.h>
#include<stdio.h>
#include<strings.h>
#include<stdlib.h>
#define DATA "I love operating systems ..."
#define BUFSIZE 1024 

void error(char *);
int main(int argc, char *argv[])
{
   int sock, length, n;
   struct in_addr *hostaddr;
   struct sockaddr_in server;
   struct hostent *hp, *gethostbyname();
   char buf[BUFSIZE];

   
   if (argc != 3) { 
         printf("Usage: server port\n");
         exit(1);
   }
   sock= socket(AF_INET, SOCK_DGRAM, 0);
   if (sock < 0) error("socket");

   server.sin_family = AF_INET;

   hp = gethostbyname(argv[1]);
   if (hp==0) error("Unknown host");

   hostaddr =(struct in_addr *) hp->h_addr;
   bcopy((char *)hostaddr, 
        (char *)&server.sin_addr,
         hp->h_length);
   server.sin_port = htons(atoi(argv[2]));
   length=sizeof(struct sockaddr_in);
   n=sendto(sock,DATA,30,0,(struct sockaddr *)&server,length);
   if (n < 0) perror("Sendto");
   n = recvfrom(sock,buf,BUFSIZE,0,(struct sockaddr *) &server,&length);
   if (n < 0) error ("recvfrom");
   buf[n]='\0';
   printf("The return message was %s\n",buf);
   return 0;
}

void error(char *msg)
{
    perror(msg);
    exit(0);
}