What does your testing show?

It may sound obvious, but FTP requires an FTP client at one end of the
communication and an FTP server at the other.  There are no limits to the
size of a file sent via FTP.  However, FTP, by itself, it not secure.  There
is a secure variant of FTP that uses SSL, but you won't get there with
socket programming.  For that, I'd recommend you buy a component.  The SSL
handshake is a bit complicated.

So, as long as your VB app is running on a client machine, you can use FTP
to upload large files in an non-secure manner.

There is a protocol called SSH that will allow files to be copied securely
(it is not FTP, but it is secure file transfer).  You would need an SSH
server at one end and an SSH client at the other... all of this is open
source.

HTH,
--- Nick