//-------------------------------------------------------------------
//	tcpstress.cpp
//
//	This modification of our earlier 'tcpclient.cpp' establishes
//	a rapid succession of connections and data-exchanges with an
//	echo-server, in order to reveal design-flaws in the server's
//	responsiveness or in its disposition of any child-processes.
//
//	     to compile:  $ g++ tcpstress.cpp -o tcpstress
//	     to execute:  $ ./tcpstress <hostname>
//
//	programmer: ALLAN CRUSE
//	written on: 11 MAR 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 that 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;

	//-----------------------------------
	// initialize our connection counter 
	//-----------------------------------
	int	count = 0;

	//-----------------------------------------------------------
	// main loop to initiate a rapid succession of many separate
	// server connections, exchanges-of-data, and disconnections 
	// in order to stress-test that server's adequacy under load
	//----------------------------------------------------------- 
	while ( ++count < 10000 )
		{
		//------------------------------------------------
		// construct the message to be sent to our server 
		//------------------------------------------------
		char	msg[ 80 ] = { 0 };
		int	len = sprintf( msg, "This is message number " );
		len += sprintf( msg+len, "%d \n", count ); 


		//---------------------------------------------------
		// 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 < len; 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 };
		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 );
		}
	printf( "\n" );	
}