supplier.c

#include <stdio.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <stdlib.h>


int main(int argc,char *argv[]){

	// Memory structure to represent message in queue
	struct {
		long priority;
		int number;
	} msgp;

	// Instantiate queue item
	msgp.priority= 2;
	msgp.number = 0;

	int msqid; 		// key for recieve queue
	int supplierQid;	// key for send qeueu
	int status;		// placeholder for status
	
	// Add key variables
	int msqid_key, qidSupplier_key;

	// get a key based on pwd directory R byte
	msqid_key = ftok(".", 'R');
	
	// Negative result is error
	if (msqid_key < 0)
		perror("Unable to create msqid_key\n");

	// get a key based on pwd directory and S byte
	qidSupplier_key = ftok(".", 'S');

	// Negative result is error
	if ( qidSupplier_key < 0)
		perror("Unable to create qidSuppler_key\n");

	//~ Create a Q for receiving information (you can use key
	//~ as unique identifier)
	msqid = msgget( msqid_key, 0660 | IPC_CREAT);

	//~ Create a Q for sending information to the requester
	//~ (you can use key-1 as the unique identifier)
	supplierQid = msgget( qidSupplier_key, 0660 | IPC_CREAT);

	//~ Loop
	while ( 1 ) {

		//~ Receive number from requester
		status = msgrcv(msqid ,&msgp,sizeof(msgp)-sizeof(long),2,0);
		
		if ( status >= 0 ) {
			//~ Calculate square of that number
			msgp.number = msgp.number * msgp.number;

			//~ Send that calculated number back to the requester    
			status = msgsnd( supplierQid, &msgp, sizeof(msgp)-sizeof(long), 0);

			if ( status ) {
				printf("Error sending message to requester.\n");
				return -1;
			}
		} else {
			printf("Error receiving message from requester.\n");
			return -1;
		}
	}

	return 0;
}