Seventh step complete:
Test client and server (named "Durable" :) ) working (using length prefixing)... Server listens for incoming connections, receives packet data from test client, and parses it as individual packets of various sizes. Broadcasting packets out to all clients not yet done, and packet types not yet implemented either (integer is currently hardcoded).
I then expanded the test client code to intermingle connections, data transfers, and disconnections among each other, and it still worked perfectly:
Yay!
Next steps for server: determining various packet types and broadcasting fully received packets to all clients. Eventually there will need to be actual "packet info types" (representing, "What does this packet tell me about the game?") and responses to those info types (like updating a player's position or displaying a chat message). This may or may not even be considered on the server side.
Also, it seems that much of the previous graphics code was done using obsolete OpenGL commands. Some learning and work will be required to use the newer and better commands.