/* Compile: gcc socket_client.c -lnsl -lsocket -o socket_client */
/* Usage: for example, socket_client cs 6500 Hello */
/*                     socket_client 193.167.42.127 6500 "Hello again" */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

main(argc,argv) int argc; char **argv;
{
  int sock,len,N;
  struct sockaddr_in server;
  struct hostent *hp, *gethostbyname();
  char buff[1024];

  if (argc != 4) {
    fprintf(stderr,"usage: %s host port data\n",argv[0]);
    exit(1);
  }
  /* Create a socket */
  /* AF_INET = address family Internet domain  */
  /* SOCK_STREAM = communication semantics     */
  /* Protocols, see /etc/protocols */
  sock=socket(AF_INET, SOCK_STREAM, 0);
  if (sock < 0) { perror("opening socket"); exit(1);}
  /* Find the IP-address for a name */
  /* gethostbyname returns a structure of tyoe hostent for a given hostname */
  /* See netdb.h or man gethostbyname for a definition on a structure */
  /* hp contains a structure */
  hp = gethostbyname(argv[1]);
  if (hp == 0) {
    fprintf(stderr,"unknown host [%s]\n",argv[1]); exit(1);
  }
  /* Set address family, IP-address, and a port number to structure */
  /* sockaddr_in (server) */
  /* bcopy copies  the  first  n bytes of the source string src to the */
  /* destination string dest. */
  /* void bcopy (const void *src, void *dest, size_t n); */
  bcopy((char *)hp->h_addr, (char *) &server.sin_addr, hp->h_length);
  /* set domain */
  server.sin_family=AF_INET;
  /* Next change the order of bytes to order of network standard */
  /* The  htons() function converts the short integer hostshort */
  /* from host byte order to network byte order. */
  if (atoi(argv[2]) != 0)
    server.sin_port = htons(atoi(argv[2]));
  else
    /* default port */
    server.sin_port = htons(6500);
  /* Send a request to a server */ 
  if (connect(sock,(struct sockaddr *) &server,
            sizeof(struct sockaddr_in)) < 0)
    {
      perror("sending"); exit(1);
    }
  
  /* Now connection is open. Now you can write to socket as writing to a file*/
  N=strlen(argv[3]);
  if (write(sock,argv[3],N+1) != N+1) {
    perror("sending"); exit(1);
  }
  /* Close connection (socket) */
  close(sock);
  exit(0);
}