A couple things ...
1. I find port checking websites unreliable. If you say it's not open because a port checking website says so, I would not trust that. If you say it's not open because your friend can't connect to your server, then that is more reliable.
2. Is there anything else that could be stopping traffic on that port. Do you have another "box" (router or modem) before the Huawei? Does the computer you are running the server on have a firewall (most Windows computers do)?
3. Is you server working? Are you able to connect to it from a computer on your network.
4. The B315 is sometimes sold together with LTE internet connections. Most mobile carries block ports. Could your ISP be blocking you?