High level design:

My server and client use a Go-Back-N pipelined protocol. I divided
the protocol into three main parts: handshaking, pipelining, and
terminating the connection. Each part generally consisted of
looping until the required messages were sent to terminate that
stage of the protocol, allowing for both the server and client
to respond to repeated messages (eg. the server responding to a 
second SYN from the client while handshaking). To resend packets,
I used a circular queue of the 10 most recent packets into order
to resend data.

The main issue I ran into was preventing loss, as it is easy to be
off by a sequence number or resend the wrong packets upon timeout.