ORA-30683: failure establishing connection to debugger

If you getting the ORA-30683 error when attempting to connect database via SQL Developer:

Connecting to the database ORCLDB.
Executing PL/SQL: CALL DBMS_DEBUG_JDWP.CONNECT_TCP( '192.168.121.104', '54070' )
ORA-30683: failure establishing connection to debugger
ORA-12535: TNS:operation timed out
ORA-06512: at "SYS.DBMS_DEBUG_JDWP", line 68
ORA-06512: at line 1
Process exited.
Disconnecting from the database ORCLDB.

Execute below command then try to connect again.

GRANT DEBUG CONNECT SESSION TO <USER>;
GRANT DEBUG ANY PROCEDURE TO <USER>;

BEGIN
 DBMS_NETWORK_ACL_ADMIN.APPEND_HOST_ACE(
 host => '192.168.121.104',
 lower_port => null,
 upper_port => null,
 ace => xs$ace_type(
         privilege_list => xs$name_list('jdwp'),
         principal_name => '<USER>',
         principal_type => xs_acl.ptype_db
        )
 );
END;

select * from dba_network_acl_privileges where principal = '<USER>' and privilege = 'JDWP' order by acl, aclid, privilege;