Use real TCP sockets instead of AF_UNIX socketpair so TCP_NODELAY
succeeds during init() and the benchmark exercises the full write
path. Replace hardcoded message type 38 with SensorStateResponse::MESSAGE_TYPE.
Avoid benchmarking heap allocation by pre-reserving the buffer
to typical TCP MSS size and reusing it across iterations, matching
real-world usage where the buffer persists across writes.
J. Nick Koston