Strange networking issue possibly regarding Windows 10

[AdamN]

(05-09-2021 08:29 AM)Somonkin Wrote:  Ah, it was admittedly quite an oversight that we didn't try one of the test builds. We were greeted with a new error which I don't think is in 1.11.3: "Data from incorrect port" followed by Friend B's Mac address. I'm not entirely sure what the error means, but I concluded it meant the issue was port related, not OS related as I originally thought. The main reason I was weary of the OS at first is simply because it's caused issues in the past (infinite loading was mentioned, and I recall PSP2 having that issue with most Windows 7 computers, though that seems to be fixed in the later builds now as I no longer infinite load).

After messing around a bit more with a VPN, we were able to get it to work with him on Windows 10. I think the issue is most definitely that his ports are blocked, though I'm uncertain why we were still able to connect to his server when he hosted it previously (our IPs did show up in his logs, etc). It's just that despite being able to successfully connect to his server, we were unable to actually see each other. I'm assuming that perhaps port 27312 was allowed but the rest of the necessary ports for the games weren't. I was initially confused by this since Friend A only had 27312 forwarded, so I thought the issue would affect him as well if it was an issue of certain ports not being forwarded. It turns out that he has DMZ enabled, though, so I think that explains that.

Anyways, yes, it all seems good now, and we can get it to reliably work. I'll look into what he can do about his ports. For now, the VPN will do. He's from another country and his router settings are difficult to comprehend.

Thank you both for your help!

Hmm.. that is strange, "Data from incorrect port" was not supposed to happen on Windows vs Windows multiplayer, it was a rare and strange situation i had when playing Android vs Windows.
That error means that the data supposed to be sent from a certain port but upon arrival it was detected to be coming from a different port, thus the data is considered as unknown and being ignored, which certainly will cause some issue on lobby (it was related to AdhocMatching).
It happened when i was using Port Offset 5000, but after changing it to 10000 "Data from incorrect port" never occurred, which is strange.
May i know what port offset value you're using when you saw this message?

This should explain the cause of unable too see any room, infinite loading, or disconnection during lobby upto starting the mission, because we currently faking ACK packet on AdhocMatching that was supposed to be a signal to tell the sender that the data has been received successfully, so if that data is lost/dropped/ignored the sender didn't know about it and ended with desync.

Normally, when A send to B, and B received data from A, B should send ACK to A so A will know that the data is lost or not, and A can try to resend again if it was lost (if it didn't get that ACK after a certain timeout), with faked ACK and the data happened to be lost/dropped/ignored(due to wrong port) B never received the data sent by A and keep waiting for it, but A is thinking it was successfully sent and move on to send the next data (which is not what B is expecting)

The old AdhocMatching code is faking this ACK making the sender always thinking that the data was sent successfully, while it could be lost in reality, and this old code was the one used by pro-online client too, so changing this behavior to not-faking it on PPSSPP side could result to incompatibility with old/legacy pro-online (because they are faking the ACK too)