how to receive the large data using recv()?

Question

i developed client server program using c++,so i want to receive more than 500kb , my client message is terminated with "!" ,so i want to receive until my last byte(!) receive , this is my code it doesn't work.what is wrong with it.

do
  {
  int num = recv(*csock,  buf, bytesLeft,0);

if (num == 0)
{
  break;
}
else if (num < 0 && errno != EINTR)
{
  fprintf(stderr, "Exit %d\n", __LINE__);
  exit(1);
}
else if (num > 0)
{
  numRd += num;
  buf += num;
  bytesLeft -= num;
  fprintf(stderr, "read %d bytes - remaining = %d\n", num, bytesLeft);
}

  }

    while (bytesLeft != 0);
   fprintf(stderr, "read total of %d bytes\n", numRd);

Answer 1

Do you need all 1MB+ of data in one contiguous byte buffer? If so, and you stick with that protocol that has a terminating '!' and does not have a header that includes the length, then you ar stuck with memcpy() and realloc() a lot or some other buffer type like std::vector which, really just does the same thing.

If you don't need all those bytes in one string, you can store them in some other way, eg. a vector of *buffer, and so avoid copying.