//-------------------------------------------------------------------
//	slowecho.cpp
//
//	This is a TCP echo-server which sends back the characters it
//	receives from a client one-byte-at-a-time, but after a timed 
//	delay between each transmission, for demonstration purposes.  
//	(The user may terminate this server by hitting <CONTROL>-C.)
//
//	       to compile:  $ g++ slowecho.cpp -o slowecho
//	       to execute:  $ ./slowecho
//
//	programmer: ALLAN CRUSE
//	written on: 27 FEB 2009
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read(), write(), close() 
#include <netinet/in.h>	// for socket(), bind(), listen(),  
#include <time.h>	// for nanosleep()


#define DEMO_PORT	54321


int main( int argc, char **argv )
{
	//---------------------------------------------------------
	// check for a user-specified time-delay (in microseconds) 
	//---------------------------------------------------------
	if ( argc == 1 )
		{
		fprintf( stderr, "usage: ./slowecho <microseconds> \n" );
		exit(1);
		}
	long	microseconds = atol( argv[1] );
	long	nanoseconds = microseconds * 1000L;
	struct timespec	myts;
	myts.tv_sec = nanoseconds / 1000000000L;
	myts.tv_nsec = nanoseconds % 1000000000L; 

	//--------------------------------------------------
	// create a socket-address structure for our socket 
	//-------------------------------------------------- 
	struct sockaddr_in	haddr = { 0 };
	socklen_t		halen = sizeof( haddr );
	haddr.sin_family	= AF_INET;
	haddr.sin_port		= htons( DEMO_PORT );
	haddr.sin_addr.s_addr	= htonl( INADDR_ANY );

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

	//-----------------------------------------------------
	// bind this listening socket to our fixed port-number
	//----------------------------------------------------- 
	if ( bind( sock, (sockaddr*)&haddr, halen ) < 0 )
		{ perror( "bind" ); exit(1); }

	//-----------------------------------------------------
	// create a connection queue for this listening socket 
	//-----------------------------------------------------
	if ( listen( sock, 5 ) < 0 ) 
		{ perror( "listen" ); exit(1); }

	//------------------------------------------------
	// enter the main look to process client requests
	//------------------------------------------------ 
	do	{
		printf( "\nserver is listening on port %u \n", DEMO_PORT );

		//--------------------------------------------------
		// accept the next connection-request from a client
		//--------------------------------------------------
		struct sockaddr_in	paddr = { 0 };
		socklen_t		palen = sizeof( paddr );
		int	conn = accept( sock, (sockaddr*)&paddr, &palen );
		if ( conn < 0 ) { perror( "accept" ); exit(1); }

		//--------------------------------------------------
		// we can now receive characters sent by the client 
		//--------------------------------------------------
		int	star = '*';
		do	{
			int	inch = 0;
			int	i = read( conn, &inch, 1 );
			if ( i == 0 ) break;
			if ( i < 0 ) { perror( "read" ); exit(1); }
			if ( nanosleep( &myts, NULL ) < 0 ) 
				{ perror( "nanosleep" ); exit(1); }
			int	j = write( conn, &inch, 1 );
			if ( j < 0 ) { perror( "write" ); exit(1); }
			write( 1, &star, 1 );
			}
		while ( 1 );
		printf( "\n" );		

		//----------------------------------------------------
		// flush the output buffers and close this connection
		//----------------------------------------------------
		fflush( fdopen( conn, "rw" ) );
		close( conn );
		printf( "data was received, processed, and returned\n" );
		}
	while( 1 );
}