Add Network Emulation features (latency, packet loss, throttling)

addmix commented 2 years ago

Describe the project you are working on

A multiplayer VR PVP flight simulator.

Describe the problem or limitation you are having in your project

There is a complete inability to locally test inclement network conditions (latency, packet loss, etc) when running multiple instances of a game, but this is mostly limited to the lack of driver-level network emulators available for Windows 10.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

It would add debugging tools for Network Emulation,

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

The "Network Debug" tools would have a global toggle, to enable/disable debugging of inclement network conditions.

Each tool would have an option to enable/disable, and apply each of these tools selectively to inbound and/or outbound packets.

Latency, delays the transmission and acknowledgement of packets by a set value, or by a value bounded by a minimum and maximum.
Packet loss, given defined percentage chance, ignore sent/received packets.
Bandwidth throttling, limits the amount of data throughput transmitted/received.
Duplicate packets, given a percentage chance, duplicate sent/received packets.

diagram of network debug options

Debug

Network Debug

Selecting the "Network Debug" option will bring up a sub window diagram of network debug window

Network Debug

Enable (bool)

Latency (category)

Enable (bool) Use on inbound (bool) Use on outbound (bool) Minimum latency (float) Maximum latency (float)

Packet Loss

Enable (bool) Use on inbound (bool) Use on outbound (bool) Percentage change (float 0-1.0)

Bandwidth

Enable (bool) Use on inbound (bool) Use on outbound (bool) Inbound bandwidth (float) Outbound bandwidth (float)

Duplicate Packets

Enable (bool) Use on inbound (bool) Use on outbound (bool) Percentage change (float 0-1.0)

If this enhancement will not be used often, can it be worked around with a few lines of script?

This enhancement should be utilized during the development process of most networked programs, and does not have a convenient workaround. This proposal would implement nicely to the base packet transmission/retrieval system of Godot, to then effect all network communications.

Is there a reason why this should be core and not an add-on in the asset library?

This necessitates the prevention and/or delay of packets at the PacketPeer level, before the packets can be evaluated by higher-level networking components, so this functionality cannot be achieved without modification of the core.

arkology commented 2 years ago

Looks like it should be done as extension and not in core by default.

Calinou commented 2 years ago

Looks like it should be done as extension and not in core by default.

I'm not sure if this can be implemented by an extension, especially if you want it to work with all networking APIs (StreamPeer, PacketPeer, high-level multiplayer, HTTPClient, WebSockets, WebRTC, …).

addmix commented 1 year ago

Clumsy 0.3 (Available here: https://jagt.github.io/clumsy/) is a suitable stand-in for this feature.

pilot51 commented 11 months ago

I disagree. Clumsy is only available for Windows.

addmix commented 11 months ago

I disagree. Clumsy is only available for Windows.

Linux has netem which should be more capable than Clumsy, although I have not tested it. https://wiki.linuxfoundation.org/networking/netem

Calinou commented 11 months ago

netem and similar solutions tend to be annoying to work with if you don't have root permissions on your machine (also for sandboxed uses like Flatpak), so there may still be some use to having something built-in Godot for this.

I'd also like this to be built-in so the implementation can be more consistent across platforms (otherwise, each tool for each platform may have an inconsistent feature set).

rcjoel2019 commented 9 months ago

Posting a snippet for anyone on linux trying to simulate latency on localhost (netem and root permission required)

enable:

sudo tc qdisc add dev lo root handle 1: htb default 12
sudo tc class add dev lo parent 1:1 classid 1:12 htb rate 56kbps ceil 128kbps
sudo tc qdisc add dev lo parent 1:12 netem delay 150ms

disable:

sudo tc qdisc del dev lo root

Simple to get it running, but I highly recommend studying it to simulate exactly what type of network problem you want

bennicus commented 8 months ago

Clumsy 0.3 (Available here: https://jagt.github.io/clumsy/) is a suitable stand-in for this feature.

I took a quick look at the clumsy docs, it looks like it doesn't support UDP, and also doesn't work with loopback, both of which will probably be peoples most common use case for testing their multiplayer code.

143mailliw commented 7 months ago

It's also worth noting that sch_netem isn't available on some distros, so there's not really anyway to do this on, for example, Arch.

godotengine / godot-proposals