//-------------------------------------------------------------------
//	trychat.cpp
//
//	This experimental version of our 'nicchat.cpp' application
//	broadcasts each keystroke to all the other stations on our 
//	local network (but places a value in the type/length field 
//	of the packet's ethernet-header that causes those messages
//	to be discarded by customary network software).  Note that  
//	this program uses our 'withpoll.c' device-driver services. 
//
//	programmer: ALLAN CRUSE
//	written on: 24 APR 2005
//-------------------------------------------------------------------

#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 memset(), memcpy()
#include <termios.h>	// for tcgetattr(), tcsetattr()
#include <netinet/in.h>	// for ntohs(), htons()
#include <sys/ioctl.h>	// for ioctl()

#define CHAT_ID 0x0635	// identifier for our protocol

typedef struct	{
		unsigned char	dst[6];
		unsigned char	src[6];
		unsigned short	typlen;
		unsigned short	nbytes;
		unsigned char	inch[48];
		} CHAT_FRAME;

void handle_kbd_input( int, int );
void handle_nic_input( int );

char devname[] = "/dev/nic";
char devaddr[ 6 ];
int done = 0;

int main( int argc, char **argv )
{
	// open device-file and obtain device's hardware-address
	int	nic = open( devname, O_RDWR );
	if ( nic < 0 ) { perror( devname ); exit(1); }
	if ( ioctl( nic, 0, devaddr ) < 0 ) { perror( "ioctl" ); exit(1); }

	// setup our terminal for noncanonical input-mode
	struct termios	orig_term;
	int	kbd = STDIN_FILENO;
	tcgetattr( kbd, &orig_term );
	struct termios	work_term = orig_term;
	work_term.c_lflag &= ~( ECHO | ICANON );
	work_term.c_cc[ VMIN ] = 1; 
	work_term.c_cc[ VTIME ] = 0;
	tcsetattr( kbd, TCSAFLUSH, &work_term ); 

	// main program loop to handle multiplexed device-input
	do 	{
		fd_set	readset;
		FD_ZERO( &readset );
		FD_SET( nic, &readset );
		FD_SET( kbd, &readset );
		if ( select( 1+nic, &readset, 0, 0, 0 ) < 0 ) break;
		if ( FD_ISSET( kbd, &readset ) ) handle_kbd_input( kbd, nic );
		if ( FD_ISSET( nic, &readset ) ) handle_nic_input( nic );
		}
	while ( !done );	

	// restore our terminal's original settings
	tcsetattr( kbd, TCSAFLUSH, &orig_term ); 
	printf( "\n" );
}

void handle_nic_input( int nic )
{
	CHAT_FRAME	msg = {0};

	// reads next message received by the network interface
	int	nbytes = read( nic, &msg, sizeof( msg ) );

	// disregard the message if not sent by our application	
	if ( ntohs( msg.typlen ) != CHAT_ID ) return;

	// otherwise echo the message's keystroke to the screen	
	write( STDOUT_FILENO, msg.inch, msg.nbytes );	
}

void handle_kbd_input( int kbd, int nic )
{
	unsigned char	inch[ 8 ] = {0};

	// reads the next keystroke typed by the local user
	int	nbytes = read( kbd, inch, sizeof( inch ) );
	if ( nbytes < 0 ) return;

	// echo the keystroke to the local display screen
	write( STDOUT_FILENO, inch, nbytes );

	// also transmit this keystroke to other stations
	CHAT_FRAME	msg = {0};
	memset( msg.dst, 0xFF, 6 );	// dest'n address
	memcpy( msg.src, devaddr, 6 );	// source address
	msg.typlen = htons( CHAT_ID );	// set type field
	msg.nbytes = nbytes;		// count of chars 
	memcpy( msg.inch, inch, nbytes );   // copy bytes		
	write( nic, &msg, sizeof( msg ) );  // to network

	// set 'done' flag if <ESCAPE>-key was pressed
	if ( *(int*)inch == '\e' ) done = 1;
}