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

#define DATA "The sea is calm tonight, the tide is full . . ."

/*
 * Here I send a datagram to a receiver whose name I get from the command
 * line arguments. The form of the command line is dgramsend hostname
 * portnumber 
 */
 
main(argc, argv) 
     int argc; 
     char *argv[]; 
{ 
     int sock; 
     struct sockaddr_in name; 
     struct hostent *hp, *gethostbyname();

     /* Create socket on which to send. */ 
     sock = socket(AF_INET, SOCK_DGRAM, 0); 
     if (sock < 0) { 
          perror("opening datagram socket"); 
          exit(1); 
     } 

     /* 
      * Construct name, with no wildcards, of the socket to send to. 
      * Getnostbyname() returns a structure including the network address 
      * of the specified host. The port number is taken from the command 
      * line. 
      */ 
     hp = gethostbyname(argv[1]); 
     if (hp == 0) { 
          fprintf(stderr, "%s: unknown host0, argv[1]); 
          exit(2); 
     } 
     bcopy(hp->h_addr, &name.sin_addr, hp->h_length); 
     name.sin_family = AF_INET; 
     name.sin_port = htons(atoi(argv[2])); 

     /* Send message. */ 
     if (sendto(sock, DATA, sizeof(DATA), 0, &name, sizeof(name)) < 0) 
          perror("sending datagram message"); 
     close(sock); 
}