Managing TCP in a Multi-Client Server

[Radiance 17]

I need to write a TCP multiclient server. There's one main loop which checks for new connections and gives simple one-word responses to clients who make requests.

While 1
    Sleep(50)

    _ProcessTCPRequestsFromAllConnectedClients()
       
    $Socket = ""
    $Socket = TCPAccept($MainSocket)
    If $Socket = -1 Then ContinueLoop
    _RegisterNewUser($Socket)
WEnd

Client asks: What time is it?
Server responds: 10:41 am

The responses need to be sent as fast as possible.
Let's say a client with an older version connects and I want to send im an updated .exe which has 5 MB in size.

How would I go about sending that file to the client without slowing down the main loop too much?

The filetransfer doesn't need to be very speedy, can take as long as needed.

Any ideas welcome.

Edited October 6, 2015 by Radiance