Applier connects and writes the the applier-server, which is the server where migration happens.

EventsStreamer reads data from binary logs and streams it on.

Inspector reads data from the read-MySQL-server (typically a replica, but can be the master) It is used for gaining initial status and structure, and later also follow up on progress and changelog.

Migrator is the main schema migration flow manager.

Server listens for requests on a socket file or via TCP.