Use FTP instead of breaking through the open door.
However, using pure sockets with TCP protocol is not a problem, too. You have to design a simple
application-layer protocol instead of FTP, which can actually be simpler than FTP. As TCP is session-oriented, you can easily break the big file into smaller chunks and transmit them one by one. I don't want to give you more detail, just because you never mentioned
what have you tried so far and did not explain what you problem is. If you ask more specific question, you may get a chance to get some more help.
—SA