ZDoom multiplayer setup, troubleshooting and FAQ

[edward850]

Try not enabling net_ticbalance. It's using a rather raw timer that only works properly if everything else is on time. This seems to stem from an issue with how the arbitrator controls tic creation, but I haven't been able to change anything about that with the current buffer set up the way it is (there isn't a lot of leg room with the current tic command packing).

Meanwhile, this is a very horrific command-line setup you have. Let's clean it up:

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start gzdoom -iwad doom2.wad -host 2 -extratic -skill 4 -file MM.WAD MMMUS.WAD brutalv20.pk3 smivhudwidescreen.wad +sv_noweaponspawn 1 +sv_weaponstay 1 +sv_samespawnspot 1 +sv_allowjump 1 +sv_doubleammo 1

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start gzdoom -iwad doom2.wad -join 1.2.3.4 -file MM.WAD MMMUS.WAD brutalv20.pk3 smivhudwidescreen.wad

• -netmode 0 is implied.
• You could probably just swap in +dmflags 2228228 +dmflags2 4160, without all the gameplay settings.
• You do not need to repeat dmflags and other such gameplay settings on a guest node. They are already going to receive that information.
• cl_noprediction and cl_predict_specials are archived, and in the network settings menu. You don't need to constantly set them.

[Agitatio]

• -netmode 0 is implied.
• You could probably just swap in +dmflags 2228228 +dmflags2 4160, without all the gameplay settings.
• You do not need to repeat dmflags and other such gameplay settings on a guest node. They are already going to receive that information.
• cl_noprediction and cl_predict_specials are archived, and in the network settings menu. You don't need to constantly set them.

• Just wanted to be sure.
• Does it really matter though? Seeing individual commands is kind of convenient.
• Read somewhere that you better do that to avoid any issues that might arise. Guess I read wrong.
• Again, just wanted to be sure.

[edward850]

Read somewhere that you better do that to avoid any issues that might arise. Guess I read wrong.

I'd like to figure out where this keeps coming from, because it's not the first I heard of this myth, and it's still as wrong as it has always been. Heck even Vanilla synced gameplay settings.

[phantombeta]

@edward850
Probably from the same place as the game using raycasting, having swingshots and Zandronum's netcode being better than ZDoom's netcode. (People can't just stop being idiots even after being told that the problem is that their routers go crazy when ZDoom tries to do shit, even with the fact that it has been 100% confirmed that some routers are completely [censored word].)

I bet this shit came from the Skulldronum forums :v

[wildweasel]

(... even with the fact that it has been 100% confirmed that some routers are completely [censored word].)

I'd say it's a rare router indeed that isn't completely [censored word].

[the machine]

What do you use for the IP address if you want to join a game through the Internet on a different router? Is it the router IP, that of the host, some combination of the two, or something else entirely?

[wildweasel]

The easiest way to tell which IP address to use is to have your host visit a page like IP Chicken and then message you the number it gives them.

[the machine]

This only give the router IP. Is that sufficient? Or is the "name address" what goes in the arguments?

[wildweasel]

This only give the router IP. Is that sufficient? Or is the "name address" what goes in the arguments?

The router's IP should be enough.

[edward850]

To cover the base, it's whatever the guest needs to send data to.
so using this example:
Guest -> The Internet -> Host's Gateway/Router -> Host
The gateway of the host is what you'd need to address of (as wildweasel pointed out, the router's IP). It then becomes that router's job to forward data to the host machine, typically done via port forwarding.
It's also the only IP address the guest can actually contact. If the host is behind a gateway and not a 1:1 NAT, that computer would have a local IP assigned (192.168.*.*). Simply put, this address is non-existent over the Internet, and cannot be contacted over it.

[Agitatio]

Can't find any info about Prediction Lerp Scale and Lerp Threshold. What are these?

[edward850]

Controls prediction interpolation. The scale is how large of a step each frame is, and the threshold is the cap if the distance is too small.
Also another thing I might redo. It looked okay originally, but using it recently I keep finding it to be a little... off.

[Agitatio]

Controls prediction interpolation. The scale is how large of a step each frame is, and the threshold is the cap if the distance is too small.
Also another thing I might redo. It looked okay originally, but using it recently I keep finding it to be a little... off.

What values would you recommend?

[edward850]

Its defaults are what I tuned it for. Setting the threshold too high can make the behaviour inconsistent, and the scale is really up to user preference. You might not even want it on (setting the scale to 0 will switch it off). It's a user setting for a reason.
My problem with it is at this time, it assumes all differences converge the same frame of time, which can make even 56ms (2 tics) have same rather large leaps. The scaling behaviour itself is pretty naf, and the reason why it became the off switch (as setting it too low could disrupt the prediction all together, so instead it just doesn't run if said scale is far too low).

[Arcturon]

Hello

For a while now I've been trying to set up a server for myself and two friends. I've managed to open all the proper ports and everything works when it is just two players, thanks for the guide on how to do that by the way.

However, I'm a little bit lost when it come to the UDP hole punching. I'm not quite certain what to do, I've read some articles and did some googling to find out what I need to do to hole punch, but I haven't found any guides on how to go about doing that. Any help would be really appreciated.