Designing a line protocol

advanced16 min readLesson 163 of 180

A KV exchange where every decision — frames, single-line responses, QUIT, ERR — is visible.

The checkpoint protocol — a KV store over TCP:

client: PUT key value
     server: OK

client: GET key
           server: VALUE value
   (or)  MISSING

client: QUIT
              server: BYE
  (then both close)

Design decisions worth noticing: the frame is a line (text protocol, easy to debug with telnet); responses are SINGLE lines (the client never has to count bytes); QUIT ends the session explicitly instead of relying on EOF races; unknown commands answer ERR rather than hanging or crashing. A server loop: accept → per-connection handler → read-line/write-line until QUIT/EOF. The test client proves the whole loop over real loopback bytes.

Now practice

Socket drillsFraming, budgets, and deadlines — the discipline before real sockets.2 challenges · · ~50 min