Crosstalk when playing online with 2 PCs on the same network

Crosstalk when playing online with 2 PCs on the same network

When two PCs on the same network are playing online at the same time, in separate matches, a lot of strange behavior occurs. After playing with it for a while, I believe that packets aren’t being consistently sent to the correct client.

Steps to reproduce:

  1. Have two Fantasy Strike accounts loaded on two PCs wired to the same router
  2. Have both accounts for play concurrent matches against separate opponents
    -No need to match queue times, as long as both clients end up in concurrent matches
    -Behavior seems the same whether both are in ranked or PC 1 casual, PC 2 ranked. Haven’t tested other configurations
  3. Have one of the players KO their opponent
    -For Actual Results point 3 only
    -There’s more to it, I’ve only seen it once and haven’t figured out how to reproduce since. May need to perfectly time a hit on the other PC?

Expected Results:
Both players are able to play as normal, with minimal latency.

Actual Results:

  1. Severe, intermittent latency on both machines (gameplay pausing for seconds at a time). Does not always match up between PCs, sometimes only one has the issue. Seems worse on PC 1, which has a shorter connection to the router.
  2. Dropped controller inputs
  3. At one point, the player on PC 1 KOed their opponent. At the same time, the KO notification flashed on the screen of PC 2, while both players in the match were alive. This obscured the playing field for PC 2, but the match otherwise continued as normal.

Both PCs are on a wired connection to an ASUS RT-AC1750 router. No port forwarding has been configured. We haven’t experienced similar issues in other games.

Game Version:
Steam client v1.18962

System Information:
Both PCs running up-to-date versions of WIndows 10

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I would guess that you only have one public IP address? So you’re trying to run two separate servers that (to the rest of the world) both have the same address. It’s not surprising the packets end up at the wrong one. The only way for FS to distinguish between them would be to add the feature that servers can have different port numbers. (But that opens up more issues because there would be more ports that people need to forward).

I wonder if as a work around you could somehow stop FS from running as a server at all and force it to only run as a client. Maybe if you disable UPnP in your router it would be unable to open server ports and so force this behaviour? Then you would be limited in what opponents you could connect to, but when you do connect you’d be the client and so it would work.

But I’ve never even looked at the FS network code so I might be completely wrong.

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