[luau] localhost connections

[whenever]

> the transport layer is layer 4 in OSI.  Thus, TCP/IP is a combination of
> layer 4, 3 and 2.  TCP provides two services; connection (data link), and
> transport.  IP provides the routing (network).  So to map TCP/IP to OSI
> accurately, we would need to break TCP into two pieces, and put IP in the
> middle.

TCP = Transmission Control Protocol (connection), it will re-transmit if 
missing/error packets.

UDP = User Datagram Protocol (connection-less), it will not re-transmit  
becasue there's no error checking, but will work if you application layer 
build with error checking.

TCP and UDP are encap in IP and IP layer will add it's own header before 
sending it to data link layer, then data link layer format the frame/add 
header before shipping it out.