/*********************************************
*	File name: UDPquotecnls.cpp - This program is being 
*   submitted as a part of program 1 home assignment by
*   his student bhavani prasad sangannagari (990 02 0777).	
*   main, UDPquotecnls, Errexit Modified from connectionless UDP echo
*   in class notes of Bob Cotter and public examples directory.
*	The program takes commandline arguments for a destination
*	server plus port which will send any data entered from the
*	keyboard and recieves the quote from server.
*   It uses the winsock connectionless
*	communication functions (sendto and recvfrom)
*	It terminates with a ^Z (F6 EOF) from the keyboard.
*********************************************************/


#include<iostream.h>
#include<stdio.h>
#include<winsock.h>

#define WSAver 0x102

#define LINELEN 100

void errexit(const char *, ...);
void UDPquotecnls(const char *, const char *);

/*****************************************************
* 	main ( )- UDP client for quote service
*	This routine defines defaults for server host and 
*	service, then takes command line parameters
*	as host and service.  It then calls WSAstartup ()
*	to select and initialize "winsock.dll", calls the 
*	UDPquotecnls function, and finally closes out the dll.
******************************************************/


void main(int argc, char *argv[]) {

char *service = argv[1];
char *host = argv[2];

WSAData wsadata;

 if(WSAStartup(WSAver, &wsadata))
 errexit("WSAStartup failed\n");
 
 UDPquotecnls(host, service);

 WSACleanup();

}

/**************************************************************
* 	UDPquotecnls ( ) This connectionless version embeds the host 
*	identification process within this routine.  It selects a
*	socket, and then goes into a loop, sequentially asking for
*	new input, sending it to the server (sendto ( )), looking for
*	a response (recvfrom( )), and printing the result, until an EOF
*	(^Z) (F6) is entered from the keyboard.
***********************************************************************/

void UDPquotecnls(const char *host, const char *service) {

char	buf[LINELEN+1];     		/* buffer for one line of text	*/
SOCKET	s;			                /* socket descriptor */
int	nchars;             			/* read count*/
struct hostent	*phe;	           /* pointer to host information entry	*/
struct servent	*pse;	           /* pointer to service information entry	*/
struct protoent *ppe;	           /* pointer to protocol information entry  */
struct sockaddr_in sin;            /* an Internet endpoint address 		*/
int	type, status;	               /* socket descriptor and socket type	*/
char	*transport = "udp";         /* transport service name for port	*/


 memset(&sin,0,sizeof(sin));  // initialising sockadd_in structure with 0
  sin.sin_family = AF_INET;	// sin.sin_family = AF_INET;

/* Map service name to port number */
  if (pse = getservbyname(service,transport))
	  sin.sin_port = pse->s_port;
	  
	 else if ((sin.sin_port = htons((u_short)atoi(service))) == 0 )
		 errexit("can't get \"%s\" service entry\n", service);
	 
/* Map host name to IP address, allowing for dotted decimal */

	 if (phe = gethostbyname(host))
	 memcpy(&sin.sin_addr, phe->h_addr, phe->h_length);
	
	 else if ((sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE )
         	errexit("can't get \"%s\" host entry\n", host);

/* Map protocol name to protocol number */

   if ( (ppe = getprotobyname(transport)) == 0)
      errexit("can't get \"%s\" protocol entry\n", transport);


 if (strcmp(transport, "udp") == 0)
  type = SOCK_DGRAM;
  else
  type = SOCK_STREAM;

/* Allocate a socket */

s = socket(PF_INET, type, ppe->p_proto);

   if (s == INVALID_SOCKET)
   errexit("can't create socket: %d\n", GetLastError());

/* Here user enters input which is sent to server and a quote is recieved from server */

 while (fgets(buf,sizeof(buf),stdin)) 
 { 
     buf[LINELEN]= '\0';
	 nchars = strlen(buf);

 status =  sendto(s, buf, nchars, 0,(struct sockaddr FAR *) &sin, sizeof(sin));

 if (status == SOCKET_ERROR) 
 errexit("Sendto failed: %d\n", GetLastError ());
 
  if (recvfrom(s, buf, LINELEN, 0, NULL, NULL) < 0)
   errexit("recv failed: %d\n", GetLastError());
 
  fputs(buf,stdout);
 }

}

/*******************************************************************************
* Errexit takes variable number of arguments, passes on to vprintf for output  
* and finally calls WSACleanup to release system socket resources. 
* this follows the printf conventions for the formatted output. 
********************************************************************************/

void errexit(const char *format, ...)
{
	va_list args;

	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
	WSACleanup();
	exit(1);
}