How does the socket connect timeout work?

Question

To my understanding, the socket connection timeout is controlled by the TCP transport, which uses Retransmission Timeouts (RTOs). if the the ack does not come back before timer expires, the connect request (Sync) will be retransmitted, and the RTO will be doubled.

So what is the functionality of connection timeout in Java socket when we call Socket.connect(endpoint, connectTimeout)

Answer 1

So what is the functionality of connection timeout in Java socket when we call Socket.connect(endpoint, connectTimeout)

It sets an overall timeout for the connection to have been established; i.e. it says how long the application is prepared to wait for all of the packet-level timeouts, retransmissions, etc to succeed (or not) before giving up.