1. Take time to read this entire thread instead of hoping someone will just give you the answer.
2. Follow the suggestions in the first post, and try other port forwarding programs/methods/etc.
3. As a last resort, hamachi will work for hosting duels or other events where other people will plan to join ahead of time.
4. After trying everything else and still being unable to host to the extent you want, report back here with many more details. What did you try? Did anything help at all? What type of computer are you using? What router? Were you ever able to host in the past? Can you join any server without CTOing or only servers with plus or none at all? Or any other relevant details you can think of. Your previous post doesn't give enough information for me to really be able to help.