dispatcher.c

/*-------------------------------------------------------------------------------
Final Project: Needham-Schroeder Protocol.

FILE:   dispatcher.c

Written By: 
     1- Dr. Mohamed Aboutabl
Submitted on: 12/3/17
-------------------------------------------------------------------------------*/

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>

#include "wrappers.h"

#define   READ_END	0
#define   WRITE_END	1
#define   STDIN  0
#define   STDOUT 1
//--------------------------------------------------------------------------
int main( int argc , char *argv[] )
{
    pid_t  amalPID , basimPID , kdcPID; 
    int    AtoKDC_ctrl[2] , KDCtoA_ctrl[2] , AtoB_ctrl[2] , BtoA_ctrl[2] , AtoB_data[2] ;  
    char   arg1[20] , arg2[20] , arg3[20] , arg4[20] , arg5[20];
    
	Pipe( AtoKDC_ctrl );  // create pipe for Amal-to-KDC control
	Pipe( KDCtoA_ctrl );  // create pipe for KDC-to-Amal control
    Pipe( AtoB_ctrl ) ;   // create pipe for Amal-to-Basim control
    Pipe( BtoA_ctrl ) ;   // create pipe for Basim-to-Amal control
    Pipe( AtoB_data ) ;   // create pipe for Amal-to-Basim data

    printf("\nDispatcher started and created all pipes\n") ;
    printf("Amal-to-KDC control pipe: read=%d  write=%d\n",   AtoKDC_ctrl[READ_END] , AtoKDC_ctrl[WRITE_END] ) ;
    printf("KDC-to-Amal control pipe: read=%d  write=%d\n",   KDCtoA_ctrl[READ_END] , KDCtoA_ctrl[WRITE_END] ) ;
	printf("Amal-to-Basim control pipe: read=%d  write=%d\n", AtoB_ctrl[READ_END] , AtoB_ctrl[WRITE_END] ) ;
    printf("Basim-to-Amal control pipe: read=%d  write=%d\n", BtoA_ctrl[READ_END] , BtoA_ctrl[WRITE_END] ) ;
	printf("Amal-to-Basim data    pipe: read=%d  write=%d\n", AtoB_data[READ_END] , AtoB_data[WRITE_END] ) ;

    // Create both child processes:
    amalPID = Fork() ;
    if ( amalPID == 0 )
    {    
        // This is the Amal process.
        // Amal will not use these ends of the pipes, decrement their 'count'
        close( AtoKDC_ctrl[READ_END]) ;
		close( KDCtoA_ctrl[WRITE_END]);
		close( AtoB_ctrl[READ_END]  ) ;
		close( BtoA_ctrl[WRITE_END] ) ;
        close( AtoB_data[READ_END]  ) ;
        
        // Prepare the file descriptors as args to Amal
        snprintf( arg1 , 20 , "%d" , AtoB_ctrl[WRITE_END]   ) ;
        snprintf( arg2 , 20 , "%d" , AtoB_data[WRITE_END]   ) ;
		snprintf( arg3 , 20 , "%d" , AtoKDC_ctrl[WRITE_END] ) ;
		snprintf( arg4 , 20 , "%d" , KDCtoA_ctrl[READ_END]  ) ;       
		snprintf( arg5 , 20 , "%d" , BtoA_ctrl[READ_END]    ) ;	
 
        // Now, Start Amal
        char * cmnd = "./amal/amal" ;
        execlp( cmnd , "Amal" , arg1 , arg2 , arg3 , arg4 , arg5 , NULL );

        // the above execlp() only returns if an error occurs
        perror("ERROR starting Amal" );
        exit(-1) ;      
    } 
    else
    {    // This is still the Dispatcher process 
        basimPID = Fork() ;
        if ( basimPID == 0 )
        {  
            // This is the Basim process
            // Basim will not use these ends of the pipes, decrement their 'count'
            close( AtoB_ctrl[WRITE_END] ) ;
            close( AtoB_data[WRITE_END] ) ;
			close( BtoA_ctrl[READ_END]  ) ;
            
            // Prepare the file descriptors as args to Basim
            snprintf( arg1 , 20 , "%d" , AtoB_ctrl[READ_END]  ) ;
            snprintf( arg2 , 20 , "%d" , AtoB_data[READ_END]  ) ;
			snprintf( arg3 , 20 , "%d" , BtoA_ctrl[WRITE_END] ) ;

            char * cmnd = "./basim/basim" ;
            execlp( cmnd , "Basim" , arg1 , arg2 , arg3 , NULL );

            // the above execlp() only returns if an error occurs
            perror("ERROR starting Basim" ) ;
            exit(-1) ;
        }
        else
        {   
			kdcPID = Fork() ;
			if ( kdcPID == 0 )
			{
				// This is the Basim process
            	// Basim will not use these ends of the pipes, decrement their 'count'
            	close( AtoKDC_ctrl[WRITE_END] ) ;
            	close( KDCtoA_ctrl[READ_END] ) ;
				
            	// Prepare the file descriptors as args to Basim
            	snprintf( arg1 , 20 , "%d" , AtoKDC_ctrl[READ_END] ) ;
            	snprintf( arg2 , 20 , "%d" , KDCtoA_ctrl[WRITE_END] ) ;

            	char * cmnd = "./kdc/kdc" ;
            	execlp( cmnd , "KDC" , arg1 , arg2 , NULL );
				
            	// the above execlp() only returns if an error occurs
            	perror("ERROR starting KDC" ) ;
            	exit(-1) ;
			}
			else
			{
				// This is still the parent Dispatcher  process
            	// close all ends of the pipes so that their 'count' is decremented
            	close( AtoB_ctrl[WRITE_END] ); 
            	close( AtoB_ctrl[READ_END]  );   
            	close( AtoB_data[WRITE_END] ); 
            	close( AtoB_data[READ_END]  );
				close( AtoKDC_ctrl[WRITE_END]);
				close( AtoKDC_ctrl[READ_END]);
				close( KDCtoA_ctrl[WRITE_END]);
				close( KDCtoA_ctrl[READ_END]);
				close( BtoA_ctrl[WRITE_END]);
				close( BtoA_ctrl[READ_END]);   

            	printf("\nDispatcher is now waiting for KDC to terminate\n") ;
                waitpid( kdcPID , NULL , 0 ) ;

				printf("\nDispatcher is now waiting for Amal to terminate\n") ;
            	waitpid( amalPID , NULL , 0 ) ;

            	printf("\nDispatcher is now waiting for Basim to terminate\n") ;
            	waitpid( basimPID , NULL , 0 ) ;

            	printf("\nThe Dispatcher process has terminated\n") ;     
        	}
		}
    }  
}