test2.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;

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

  if (! first) {
    close(readfd);
    close(writefd);
  } else {
    first=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) {
  if (generror==2) {
    return(-1);
  } else {
    if (write(writefd,&b,1)!=1) 
      return(-1);
    else
      return(1);
  }
}

//------------------------------------------------------------------
// layer2 prototypes

int l2_write(char *, int);
int l2_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("l2 test 1 (sending ints): ");
  for (i=0;i<1000;i++) {
    if (l2_write((char *) &i, sizeof(int) )==-1) {
      printf("l2_write error\n");
      err=1;   break;
    }

    if ( (len=l2_read(buf,100))==-1) {
      printf("l2_read error\n");
      err=1;   break;
    }

    if (len!=sizeof(int)) {
      printf("l2_read returns wrong length\n");
      err=1;break;
    }

    if (*((int *)buf) != i) {
      printf("l2_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("l2 length test 999: ");
  len=l2_write(buf,999);
  if (len==-1) {
      printf("l2_write error\n");
      err=1;
  } else {
    if (len != 999) {
      printf("l2_write returned wrong count\n");
      err=1;
    } else {
      if ( (len=l2_read(inbuf,2000))==-1) {
	printf("l2_read error\n");
	err=1;
      } else {
	if (len!=999) {
	  printf("l2_read returns wrong length\n");
	  err=1;
	} else {

	  for (i=0;i<999;i++) {
	    if (inbuf[i] != (char)(i%256)) {
	      printf("l2_read value is wrong\n");
	      err=1;break;
	    }
	  }
	}
      }
    }
  }

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

  printf("l2 forced read error: ");
  init_l1();
  generror=1;

  if ( (len=l2_read(buf,100))==-1) {
    printf("OK\n");
  } else {
    printf("doesn't return error (it should!)\n");
  }

  printf("l2 forced write error: ");
  init_l1();
  generror=2;

  if ( (len=l2_write(buf,100))==-1) {
    printf("OK\n");
  } else {
    printf("doesn't return error (it should!)\n");
  }
  return(0);
}