test3.c

this gives details of the network programming

// Netprog 2002 HW1 submission test program
// This code tests layer 4
//

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>    // read() and write() prototypes are here
//------------------------------------------------------------------
// Sample layer 1 implementation based on a unix pipe.
//

int readfd,writefd;
int generror=0;
int writecount=0;


void init_l1(void) {
  static int first=1;
  int fds[2];

  if (! first) {
    close(readfd);
    close(writefd);
  } else {
    first=0;
  }

  writecount=0;

  if (pipe(fds)==-1) {
    printf("ERROR: Can't create pipe \n");
    exit(1);
  }
  readfd = fds[0];
  writefd = fds[1];
}



// sample l1_read just calls read on stdin
int l1_read( char *b) {

  if (generror==1) {
    return(-1);
    
  } else {
    if (read(readfd,b,1)!=1) 
      return(-1);
    else
      return(1);
  }
}

// sample l1_write just calls write to stdout
int l1_write(char b) {
  writecount++;
  if (generror==2) {
    return(-1);
  } else {
    if ((generror==3) && (writecount==10)) {
      // modify only the 10th byte
      //  (aiming for the middle of the message)
      b++;
    }
    if (write(writefd,&b,1)!=1) 
      return(-1);
    else
      return(1);
  }
}

// Sample layer 2

int l2_read(char *s, int max) {
  int i;
  char buf[10];
  int len;

  // read the length as 3 ASCII digits
  for (i=0;i<3;i++) {
    if (l1_read(buf+i)==-1) {
      return(-1);
    }
  }
  //convert string to int
  buf[3]=0;
  len = atoi(buf);

  // make sure the message is not too large
  if (len>max) {
    return(-1);
  }
  // now read that many bytes
  for (i=0;i<len;i++) {
    if (l1_read(s+i)==-1) {
      return(-1);
    }
  }
  // everything seems OK
  return(len);

}

int l2_write(char *s, int n) {
  int i;
  char buf[10];

  if ((n>999)||(n<0)) return(-1);

  // first send the length as 3 ASCII digits
  sprintf(buf,"%03d",n);
  for (i=0;i<3;i++) {
    if (l1_write(buf[i])!=1) {
      return(-1);
    }
  }

  // now send the buffer
  for (i=0;i<n;i++) {
    if (l1_write(s[i])!=1) {
      return(-1);
    }
  }
  
  // everything seems fine - return n
  return(n);
}

  



//------------------------------------------------------------------
// layer3 prototypes

int l3_write(char *, int);
int l3_read(char *, int);


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

  char buf[4000];
  char inbuf[4000];
  int len;
  int err=0;

  int i;

  init_l1();

  printf("l3 test 1 (sending ints): ");
  for (i=0;i<1000;i++) {
    if (l3_write((char *) &i, sizeof(int) )==-1) {
      printf("l3_write error\n");
      err=1;   break;
    }

    if ( (len=l3_read(buf,100))==-1) {
      printf("l3_read error\n");
      err=1;   break;
    }

    if (len!=sizeof(int)) {
      printf("l3_read returns wrong length\n");
      err=1;break;
    }

    if (*((int *)buf) != i) {
      printf("l3_read value is wrong\n");
      err=1;break;
    }
  }

  if (! err) printf("OK\n");
  init_l1(); err=0;

  for (i=0;i<3000;i++) 
    buf[i]=i%256;

  printf("l3 length test 800: ");
  len=l3_write(buf,800);
  if (len==-1) {
      printf("l3_write error\n");
      err=1;
  } else {
    if (len != 800) {
      printf("l3_write returned wrong count\n");
      err=1;
    } else {
      if ( (len=l3_read(inbuf,2000))==-1) {
	printf("l3_read error\n");
	err=1;
      } else {
	if (len!=800) {
	  printf("l3_read returns wrong length\n");
	  err=1;
	} else {

	  for (i=0;i<800;i++) {
	    if (inbuf[i] != (char)(i%256)) {
	      printf("l3_read value is wrong\n");
	      err=1;break;
	    }
	  }
	}
      }
    }
  }

  if (! err) printf("OK\n");
  init_l1(); err=0;

  printf("l3 length test 1000: ");
  len=l3_write(buf,1000);
  if (len==-1) {
      printf("OK\n");
  } else {
    printf("Allows 1000 (should not)\n");
  }

  printf("l3 forced read error: ");
  init_l1();
  generror=1;

  if ( (len=l3_read(buf,100))==-1) {
    printf("OK\n");
  } else {
    printf("doesn't return error (it should!)\n");
  }

  printf("l3 forced write error: ");
  init_l1();
  generror=2;

  if ( (len=l3_write(buf,100))==-1) {
    printf("OK\n");
  } else {
    printf("doesn't return error (it should!)\n");
  }

  init_l1(); err=0;

  generror=3;
  printf("l3 transmission error test: ");
  len=l3_write(buf,30);
  if (len==-1) {
      printf("l3_write error\n");
      err=1;
  } else {
    if (len != 30) {
      printf("l3_write returned wrong count\n");
      err=1;
    } else {
      if ( (len=l3_read(inbuf,2000))==-1) {
	printf("OK\n");
      } else {
	printf("Didn't find the problem\n");
      }
    }
  }

  return(0);

}