#include<stdio.h>
#include<stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>
#include <string.h>

#define MAGIC_PORT_NUM 15000
#define BUF_SIZE 512

int main( int argc, char ** argv )
{
		char buf1[ BUF_SIZE ];
		char bytes1;
		char buf2[ BUF_SIZE ];
		char bytes2;
		int rc1;
		int io_sd1;
		int io_sd2;
		int listen_sd;
		int foo;

		struct protoent * proent_ptr = getprotobyname ( "tcp" );
		int proto_num = proent_ptr->p_proto;
		struct sockaddr_in serv;
		struct sockaddr_in client1;
		struct sockaddr_in client2;
		socklen_t cli_len = sizeof( struct sockaddr_in );
		int port_num = MAGIC_PORT_NUM;


		if ( argc > 1 )
				port_num = atoi( argv[1] );


		listen_sd = socket( PF_INET, SOCK_STREAM, proto_num );
		if ( -1 == listen_sd )
		{
				fprintf( stderr, "socket error\n" );
				exit(1);
		}
		printf( "listen_sd = %d\n", listen_sd );

		/* setup the serv sockaddr */
		serv.sin_family = PF_INET;/* match what socket got */
		serv.sin_addr.s_addr = htonl( INADDR_ANY );/* network byte order */
		serv.sin_port = htons( port_num );

		rc1 = bind( listen_sd, (struct sockaddr *)&serv, 
						sizeof( struct sockaddr_in ) );
		if ( -1 == rc1 )
		{
				fprintf( stderr, "bind error\n" );
				exit(2);
		}
		printf ( "listening on port %d\n", port_num );

		rc1 = listen( listen_sd, 10 );
		if ( -1 == rc1 )
		{
				fprintf( stderr, "listen error\n" );
				exit(2);
		}
		printf ( "listening, waiting on accept\n" );

		/* this blocks waiting for the connect from the client */
		io_sd1 = accept( listen_sd, (struct sockaddr *)&client1, &cli_len );
		if ( -1 == io_sd1 )
		{
				fprintf( stderr, "client 1 accept error\n" );
				exit(1);
		}
		printf( "io_sd1 = %d\n", io_sd1 );

		io_sd2 = accept( listen_sd, (struct sockaddr *)&client2, &cli_len );
		if ( -1 == io_sd2 )
		{
				fprintf( stderr, "client 2 accept error\n" );
				exit(1);
		}
		printf( "io_sd2 = %d\n", io_sd2 );


		/* now we can do IO */
		/*client 1 read what is typed and send to client2 */
		/*then client 2 read what is typed and send to client1 */
		foo = 1;
		while (foo)
		{
				read(io_sd1, buf1, sizeof(buf1));
				if (strcmp(buf1, "quit\n")==0) 
				{
					close( io_sd1 );
					close( io_sd2 );
					close( listen_sd );
				}
				bytes1 = sprintf ( buf1, buf1);
				write( io_sd2, buf1, bytes1 );

				read(io_sd2, buf2, sizeof(buf2));
				if (strcmp(buf2, "quit\n")==0) 
				{
					close( io_sd1 );
					close( io_sd2 );
					close( listen_sd );
				}
				bytes2 = sprintf ( buf2, buf2);
				write( io_sd1, buf2, bytes2 );
		}

		return 0;
}

...
do
   ...

while (strcmp(quit_buff, "quit\n")!=0)

		do
		{
				read(io_sd1, buf1, sizeof(buf1));
				bytes = sprintf ( buf1, buf1);
				write( io_sd2, buf1, bytes );
				
				quitTest1 = strstr(buf1,"quit");
				if (quitTest1 != NULL)
					break; /* if user types quit, break from loop */

				read(io_sd2, buf2, sizeof(buf2));
				bytes = sprintf ( buf2, buf2);
				write( io_sd1, buf2, bytes );
				
				quitTest2 = strstr(buf2,"quit");
				if (quitTest2 != NULL)
					break; /* if user types quit, break from loop */
				
		} while (1);


		/* close the connections */
		  
		  close( io_sd1 );
		  close( io_sd2 );
		  close( listen_sd );