I only have set up port 10308.
Maybe 10307 was a typo.
After adding port 10308 to your router, yxou can check on pcflank.com if that port ist stealth, closed or open.
it should at least be shown as closed only and while hosting it should be shown as open.
stealth is bad because ist not visible for the ones who want to join your session.
http://www.pcflank.com/scanner1.htm
At "Scan desired ports and/or the range of ports.
Type in the port number and/or port range, separated by commas (example: 14, 80, 200-240)."
enter port 10308 only