//-------------------------------------------------------------------
//	msgclient.cpp
//
//	This example uses the 'sendmsg()' and 'recvmsg()' functions
//	to send a message to our 'msgserver' application, then wait 
//	for up to five seconds for the expected response to arrive.  
//
//	    compile using:  $ g++ msgclient.cpp -o msgclient
//	    execute using:  $ ./msgclient <hostname>
//
//	programmer: ALLAN CRUSE
//	written on: 12 FEB 2009
//-------------------------------------------------------------------

#include <netdb.h>	// for gethostbyname()
#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <string.h>	// for strncpy()
#include <arpa/inet.h>	// for inet_ntoa()

#define SERVER_PORT	54321

int main( int argc, char **argv )
{
	//------------------------------------------------
	// get destination hostname from the command-line
	//------------------------------------------------
	char	peername[ 64 ] = { 0 };
	if ( argc == 1 ) { fprintf( stderr, "target?\n" ); exit(1); }
	strncpy( peername, argv[ 1 ], 63 );

	//--------------------------------------------------
	// obtain the internet address for this remote host
	//--------------------------------------------------
	char	peeraddr[ 16 ] = { 0 };
	struct hostent	*pp = gethostbyname( peername );
	if ( !pp ) { herror( "gethostbyname" ); exit(1); }
	strcpy( peeraddr, inet_ntoa( *(in_addr*)pp->h_addr ) );

	//--------------------------------------------------------
	// initialize a socket-address object for the remote host	
	//--------------------------------------------------------
	struct sockaddr_in	paddr = { 0 };
	socklen_t		palen = sizeof( paddr );
	paddr.sin_family	= AF_INET;	
	paddr.sin_port		= htons( SERVER_PORT );	
	paddr.sin_addr.s_addr	= *(uint32_t*)pp->h_addr;	

	//------------------------------------
	// create an internet datagram socket
	//------------------------------------
	int	sock = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); }

	//-------------------------------------
	// set a timeout for receiving replies
	//-------------------------------------
	struct timeval	mytv = { 5, 0 };
	int		tlen = sizeof( mytv );
	if ( setsockopt( sock, SOL_SOCKET, SO_RCVTIMEO, &mytv, tlen ) < 0 )
		{ perror( "setsockopt RCVTIMEO" ); exit(1); }

	//---------------------------------------------------
	// initialize objects for a message-header structure
	//---------------------------------------------------
	char	msg[] = " ABCDEFGHIJKLMNOPQRSTUVWXYZ 1234567890 ";
	int	len = strlen( msg );
	
	struct iovec	myiov[1] = { { msg, len } };

	//-----------------------------------------
	// initialize the message-header structure
	//-----------------------------------------
	struct	msghdr	mymsghdr = { 0 };
	mymsghdr.msg_name 	= &paddr;
	mymsghdr.msg_namelen 	= palen;
	mymsghdr.msg_iov	= myiov;
	mymsghdr.msg_iovlen	= 1;
	mymsghdr.msg_control	= NULL;
	mymsghdr.msg_controllen	= 0;
	mymsghdr.msg_flags	= 0;

	//-------------------------------------
	// send our message to the remote host
	//-------------------------------------
	int	tx = sendmsg( sock, &mymsghdr, 0 );
	if ( tx < 0 ) { perror( "sendmsg" ); exit(1); }
	printf( " sent %d bytes to \'%s\' (%s) \n", tx, peername, peeraddr );

	//--------------------------
	// erase our message buffer
	//-------------------------- 
	bzero( msg, sizeof( msg ) );

	//-----------------------------------
	// receive a reply (or else timeout) 
	//----------------------------------- 
	int	rx = recvmsg( sock, &mymsghdr, 0 );
	if ( rx < 0 ) perror( "recvmsg" ); 
	else	printf( " received %d bytes from", rx );
	printf( " %s \n", inet_ntoa( *(in_addr*)&paddr.sin_addr ) );
	if ( rx > 0 ) puts( msg );  
}