The format of the string is determined by the transport class.
If you use the TCP transport class, SocketTransportService, provided in the JCK the format of the string is:
<hostname>:<port_number>
(if test debuggers attach to JDWP implementation)
or
<port_number>
(if test debuggers listen for connections from JDWP implementation)
If both the test debugger and test debuggee run on the local system, you can use the "localhost" identifier as the hostname.
If you run tests in singleJVM mode, use the interview settings for the JavaTest agent as the hostname for the debugger.
An empty string address is allowed in the answer.