client/server print out array and write back - c

Question

I am using C and putty to write a client/server program.
Both c files are on the same system.
I am currently having an issue with writing back to the client the frames it is using as well as printing out my frames. It prints out 3 0 9 8 but then it starts printing out 13456756 etc.
Here is what I have:
server:
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
main (void)
{
int to_server; // to read from client
int from_server; // to write to client
int finish; // lets me know that client is done
int i,j,k,m,l; // because C needs this defined as int
int numClient;// number of clients
char temp[14];
int page_size = 128;
int pages_left;
int max_frames=10;
int used_frames =0;
int frameUpdate=0;
int freeframe[10] = {3,0,9,8,7,5,1,4,2,6}; //this is the array
int numpage=0;
int frames;
int check;
int option;
int byte;
int getPage;
int getOffset;
int physical_Addr;
int offset;
int req[3];
int again;
struct values{
char privFifo[14];
int memoryreq;
}cinput;
/* Create the fifos and open them */
if ((mkfifo("FIFO1",0666)<0 && errno != EEXIST))
{
perror("cant create FIFO1");
exit(-1);
}
if((to_server=open("FIFO1", O_RDONLY))<0){
printf("cant open fifo to write");
}
//get number of clients
printf("\nHow many clients?\n");
scanf("%d", &numClient);
for(j =1; j <= numClient; j++){
read(to_server, &cinput, sizeof(cinput));
printf("\n\nFifo_%d \nMemory request %d", &cinput.privFifo, cinput.memoryreq);
req[j-1] = cinput.memoryreq;
if((mkfifo(cinput.privFifo,0666)<0 && errno != EEXIST))
{
perror("cant create privFifo");
exit(-1);
}
if((from_server=open(cinput.privFifo, O_WRONLY)<0)){
printf("cant open fifo to write");
}
// find number of pages need for request
numpage = cinput.memoryreq/page_size;
if((numpage * page_size) < cinput.memoryreq){
numpage++;
}
sleep(1);
printf("\nPages needed %d", numpage);
write(from_server, &numpage, sizeof(numpage));
printf("\n******Main Memory******");
for(m = used_frames; m < numpage; m++){
printf("\n* client: %d\tframe: %d", j, freeframe[m]);
frames = freeframe[m];
write(from_server, &frames, sizeof(frames));
}
used_frames = max_frames - used_frames;
pages_left = max_frames - numpage;
//this is where I try to print out the available frames
printf("\n Frames available:");
for(l = pages_left; l!= 0; l--){
check = max_frames - l;
printf(" %d", freeframe[check]);
max_frames = check;
}
close(from_server);
unlink(cinput.privFifo);
}
printf("\nDONE!!!");
close(to_server);
unlink("FIFO1");
client:
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
main (void)
{
int to_server; // to write to server
int from_server;
char temp[14]; // server puts string here
int clientID;
//int frames;
int numpage;
int i;
struct values{
char privFifo[14];
int memoryreq;
}cinput;
if((to_server=open("FIFO1", O_WRONLY))<0)
printf("cant open fifo to write\n");
printf("writing data to to_server\n");
printf("Client: Please enter number of memory units: ");
scanf("%d", &cinput.memoryreq);
printf("%d", cinput.memoryreq);
clientID = getpid();
sprintf(cinput.privFifo, "Fifo_%d", getpid());
printf("\nFifo name is %s", &cinput.privFifo);
write(to_server, &cinput, sizeof(cinput));//write client pid and memUnit to server
sleep(2); //give time to send
printf("\nClient: Got the character sent, now waiting for response ");
if ((mkfifo(cinput.privFifo,0666)<0 && errno != EEXIST))
{
perror("cant create FIFO1");
exit(-1);
}
if((from_server=open(cinput.privFifo, O_RDONLY))<0){
printf("cant open fifo to write");
}
read(from_server, &numpage, sizeof(numpage));
printf("\nFrames Occupied %d", numpage);
close(to_server);
close (from_server);
unlink(cinput.privFifo);
printf ("\nall done!\n");
}
Any help is greatly appreciated. Thank you.

Answer 1

I strongly suspect the problem is the line used_frames = max_frames - used_frames;. Since used_frames is initially 0, that sets it one past the end of the array for the second iteration, so you start printing values past the end of your frame array when you run for(m = used_frames; m < numpage; m++). (By the way: please indent properly.). But set a breakpoint and run in a debugger to be sure.