The server can be debugged by using either the
-d option launches the server to one-shot mode. In this mode, the server accepts only one connection and exits after the session is disconnected. The server does not spawn a separate task for the connection.
-D option launches the server to continuous debug mode. In this mode, the server keeps on listening to the TCP port and accepts several connections. The server spawns a new task for each new connection and needs to be stopped manually when you want to finish the debugging.
The debug level is either a number, or a comma-separated list of assignments of the format
ModulePattern=debug_level, for example
"*=7,sshd2=2". Debug level 4 is usually sufficient. For more detailed information, debug level 7 can be used.