Обсуждение: [GENERAL] Streaming replication protocol

I'm trying to write a program that speaks the streaming replication protocol (for logical decoding).  I get to the part where I issue a query:

START_REPLICATION SLOT regression_slot LOGICAL 0/0;

And after that, I receive an empty copy_both_response then a copy_data that has a "Primary keepalive message" in it.  Then I'm stuck; I don't know how to respond to that.