FTP error “530 Login authentication failed”

I'm a little fuzzy on what you mean by reached the top, by which I mean did it scroll out of view or is it visible or is it exactly at the top. That said, I think the math is simple once that is answered and what you really need to do is check each div.test inside the scroll function. You can get the id or even the inner text or whatever when you need to log it.

This will tell you which ones are visible period, if you want completely visible that is a different calculation. One thing you have to keep in mind is that the scroll event fires more often than you think it does.

$('#container').scroll(function(){
    $('.test').each(function(){
        var itemOffset = Math.abs($(this).offset().top);
        var height = $('#container').height();
        if (itemOffset > 0 && itemOffset < height) {
             alert($(this).attr('id'));
        }
    });
});

fiddle over here

The most central problem with the code is that the lengths given to write() come from sizeof. If you change those to calls to strlen(), the anonymous login works. Using sizeof for the length sends 256 bytes to the server.

At least the one ftp-server I tried this with (vsftpd), did not like the password otherwise. I did not check the RFC to see if it was the length or the zeros that made it clash. For development you might also want to install some ftpd software locally. I think it might be more prudent to experiment against servers you run yourself.

NIT: I dont know what system you are compiling that code on, but on a Linux/Posix system it would require some more includes. I added

#include <string.h> 
#include <stdlib.h>
#include <unistd.h>

I suggest you compile with either the clang compiler or use the flags -Wall -Werror -Wextra to gcc.

I also suggest using strerror() or similar instead of just printing the errno, when something fails.