(RFU) Pokemon Emerald

[AeolusUX]

Union room works flawlessly! I'm just wondering if you guys tested the direct corner colosseum and trade center? I've tried both and seems it's disconnecting and giving me a communication error. Would this be the said limitation from david's blog, because the game doesn't like high latency? or the emulation of packet loss? I am playing using lan.

Edit: Actually it seems like it's a problem of the client. Only the device on client mode gets disconnected. Even tried it on relay server and same thing happened.

[ysheng26]

I haven't tried the Union room but I tried to trade on RG35XX Plus and it had this communication error as well. Best I got was to get to the trading room but when I sit down it disconnected

[papajefe]

Discovered this recently and did some testing with a friend today.

We also experienced seemingly random disconnects from the Client player. Each of us tried hosting and using the "Relay Server" features in RetroArch 1.17

Tested Union Room, Trade Center and Colosseum modes.

Union Room itself was fine, no "Connection Error" in general use.
Trade Center was able to complete a Trade once, but then "Connection Error" after.
Colosseum would usually "Connection Error" during battle load, but was able to get a few turns in sometimes.

Overall VERY cool feature that I hope to see improve as time goes on. From reading some of DavidGFs writings on the subject it sounds like at least for Pokemon Fire Red\Leaf Green\Emerald we can achieve 100% reliable netplay. Not sure about games with more real-time requirements.

[cvharris]

same thing found today. Colosseum crashes almost immediately, if not soon into the battle. Same Retroarch and gpSP versions on both devices: 1.19.1 & v1.0.0-f2837be respectively

[HaydenBYU]

I am having a similar issue but with FireRed. I keep getting communication errors at random times. I was able to see my friends trainer badge but then it crashed as we started a battle.

[gamecorner-033]

I have experienced the same communication errors as everyone above. Very cool though.

[xanat0s]

Yeah this issue has a really bad title, it has nothing to do with Emerald.

I've heard the gameboy link is hyper sensitive to desync but I'm not a hardware guy so I don't know how accurate that is. If true, that's the most likely cause and is something the devs here can do little about. It would also mean it'd work far more reliably on a local network than, say, with someone across the country.

Experiencing this on LeafGreen in the Union Room, Colosseum, and Trade Center.

[dejalavidavolar]

same error here, tested on emerald and hackroms

[gamecorner-033]

Been testing, have found that best results are when you can connect 2 devices on the same LAN and have a ping under 20.

[davidgfnet]

Unsurprisingly this only works with low latency networks. Why? Cause the original wifi adapter had people play in a 10m radius. Latency and resends were low. My implementation tries to fake collisions so cover up some latency, but this obviously breaks if the latency is too high.
Not much I can do. Unless you use mGBA or other emulators that actually do lock-step synchronization (at the cost of a very low frame rate for high latency networks).
So yeah, ideally you need to play in the same LAN or via internet in the same country (and not using proxies, these are high latency).

[AeolusUX]

Thanks for the insight! We’re still using gpsp on LAN and adjusted the check frame setting to 10, which reduced desyncs a lot for Direct Corner. It’s somewhat stable now but still disconnects occasionally on the client side. I haven't tried again recently I'm guessing there have been improvements since I originally posted this issue.

[alvaro-cuesta]

@davidgfnet thanks for your work! I'm currently studying both RA and gpSP netplay for fun.

I'm wondering: since RANP is TCP based won't artificial retransmits make the situation worse by causing more latency due to packets buffering to arrive in order?

Did you verify experimentally that it helped?

Feels like the situation would improve if RA provided UDP so you could retransmit at will without causing even more buildup of buffered TCP packets (funnily enough, it's briefly mentioned in libretro/RetroArch#10146)

[davidgfnet]

These restransmissions I talk about are "RFU" retransmissions, emulated in the RFU device. They have nothing to do with network (ie. netplay) retransmissions and such.
I know many people say that UDP could help, but building a reliable protocol on top of UDP is not easy (nor simple), just see how complex QUIC is :D And even in that case I'm not convinced this would solve the issue.
There are some issues with the RFU emulation and the way we fake some stuff, but that is tricky to find and fix.