According to
https://docs.oracle.com/en/java/javase/17/docs/specs/jpda/conninv.html

`Socket transport addresses have the format "<host>:<port>" where <host> is the host name or the IP address (may be enclosed in square brackets) and <port> is the socket port number to attach to or listen on. If <host> is empty, the local loopback address is used. If <host> equals "*" in contexts where a server is waiting for a client to attach, the server listens on all network interfaces.`

It says `the server listens on all network interfaces`, If IPV6 is supported, It actually uses IPV6, but the spec doesn't clarify that.