//-------------------------------------------------------------------
//	tcpclient.cpp
//
//	This is an implementation in C++ for the client portion of a
//	demo-program suggested by our course textbook's Java example
//	by Kurose and Rose.  The client accepts a short message that
//	a user types in, establishes a connection with a server, and
//	transmits the message's characters one at a time in order to
//	demonstrate the socket's input-buffering, then receives each
//	character that the server sends back, closes the connection,
//	and displays all of the characters it successfully received.  
//
//	     to compile:  $ g++ tcpclient.cpp -o tcpclient
//	     to execute:  $ ./tcpclient <hostname>
//
//	programmer: ALLAN CRUSE
//	written on: 22 FEB 2009
//-------------------------------------------------------------------

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

#define DEMO_PORT	54321


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

	//--------------------------------------
	// obtain the IP-address for the server
	//-------------------------------------- 
	struct hostent	*pp = gethostbyname( peername );
	if ( !pp ) { herror( "gethostbyname" ); exit(1); }

	//--------------------------------------------
	// construct a socket-address for this server
	//-------------------------------------------- 
	struct sockaddr_in	paddr = { 0 };
	socklen_t		palen = sizeof( paddr );
	paddr.sin_family	= AF_INET;
	paddr.sin_port		= htons( DEMO_PORT );
	paddr.sin_addr.s_addr	= *(int32_t*)pp->h_addr;

	//---------------------------------------------------------------
	// prompt the user for the input-message and accept the response
	//--------------------------------------------------------------- 
	printf( "\nPlease type a short sentence on the line below: \n" );
	char	msg[ 80 ] = { 0 };
	int	n = read( STDIN_FILENO, msg, sizeof( msg ) );

	//---------------------------------------------------
	// create a socket for communication with the server
	//--------------------------------------------------- 
	int	sock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );
	if ( sock < 0 ) { perror( "socket" ); exit(1); }

	//----------------------------------------
	// establish a connection with the server 
	//---------------------------------------- 
	if ( connect( sock, (sockaddr*)&paddr, palen ) < 0 )
		{ perror( "connect" ); exit(1); }

	//-------------------------------------------------------
	// write the message-characters to the socket one-by-one
	//-------------------------------------------------------
	for (int i = 0; i < n; i++)
		if ( write( sock, msg+i, 1 ) < 0 )
			{ perror( "write" ); break; }
	
	//----------------------------------------------
	// shut down the writing end of this connection
	//----------------------------------------------- 	
	fflush( fdopen( sock, "rw" ) );
	if ( shutdown( sock, SHUT_WR ) < 0 ) perror( "shutdown" ); 

	//-----------------------------------------
	// receive all the replies from the server
	//----------------------------------------- 		
	char	buf[ 128 ] = { 0 };
	int	len = sizeof( buf );
	for (int i = 0; i < len; i++)
		{
		int	rx = read( sock, buf+i, 1 );
		if ( rx < 0 ) { perror( "read" ); break; }
		if ( rx == 0 ) break;
		}

	//--------------------------------------------------
	// close the socket and release its file descriptor 
	//--------------------------------------------------
	if ( close( sock ) < 0 ) perror( "close" );
	
	//-------------------------------------------------
	// display the characters received from the server 
	//------------------------------------------------- 
	puts( buf );
}