Factorio Forums

Raising as a potential bug, but due to it's nature, it might not be Factorio's issue.

Was playing with a friend the other night and decided it'd be cool if he could jump into my game briefly to have a look around before I visit his (we're both playing from the same map seed, and seeing how we tackle issues differently). So I host the game from a saved file, as we always have in these situations, and for our joint map on 0.16 stable, it appears on the public game list, but he was unable to join as Factorio wasn't able to ping me. This was strange, but network issues happen from time to time, so I tried joining him instead but got the same issue.
I decided to try out on a public server and was able to join instantly, shortly followed by my friend. I'm not sure how the public games / servers work in Factorio, whether they are hosted by either of our computers, or a server is utilised remotely using our save file, but for some reason we weren't able to join each other, but were fine with the public servers.

Other notes:
- This was the first time we had tried online multiplayer since we both updated from 0.16 stable to 0.17.60, so unsure if this was the cause.
- Don't have a log file at the moment as have played many sessions since then. I'm hoping he'll be back online tomorrow, but if we aren't able to join each other, I'm not sure if anything will get into the file anyway?
- Both using MacOS, I'm on 10.14.6 and believe he is too, but can't say for certain.
- Both definitely using Factorio 0.17.60.
- Did try reverting back to 0.16 stable to test versions at the time, but were met with different startup errors due to new capability in the config files. I lost achievement progress as a result, and he lost GUI settings. Needless to say, probably won't try rolling back again in a hurry!

If any more information is required, please just let me know.

So a long awaited update on this, we've both been busy and not able to play together for some time, however we're still unable to play each others multiplayer save. Now both running 0.17.69, server can have a password or not, player limit not an issue, and "verify player identities" makes no difference either.

Can join other servers absolutely fine.

Anything else I can try?

That sounds like general networking issues which might be a result of your routers you use to access your internet. You need to configure them to forward incoming traffic to your machine. That is usually disabled for security reasons and needs to be enabled for the specific ports and protocols used. Consult your router's manual for details.

https://wiki.factorio.com/Multiplayer#S ... layer_Game has the necessary (default) ports for factorio and their protocols

EDIT to add: mind, only the person *hosting* the game needs to modify his router's setting. The people joining a game need not take any special action.

Thanks for the reply, some more googling after posting this determined the same, but port forwarding on my router made no difference. We suspected it was mine because I’d been having issues and changing settings.

Got him to set up on his and voila it worked! Not sure why it suddenly became an issue having worked for months previously, but hey ho. Apologies for even suspecting Factorio! Lmao