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Hi, I'm a member of the WebRTC team at Google, and I wrote a lot of the data channel and network code that's part of that behemoth. I'm glad you got this to wo

Hi, I'm a member of the WebRTC team at Google, and I wrote a lot of the data channel and network code that's part of that behemoth. I'm glad you got this to work :). I've always hoped someone would do exactly what you've done (use the data channel code on a server to do low-latency client<->server communication). We're aware of the difficulty and are actively working on making it easier to work with just he components you need for data channels (ICE, DTLS, and SCTP). It might take a while, but it's one of our goals.

shazow 10y ago
I've been trying to find some numbers on what kind of performance characteristics for using WebRTC unreliable datachannels (compared to the spectrum between pure UDP vs WebSockets). Do you know of any such comparisons? Or any intuition on the matter?
comboy 10y ago
Where does the low latency in WebRTC come from? Is it just packet ordering in TCP or is there something more to it?
- Franciscouzo 10y ago
  You can't do packet reordering on top of TCP as it is already ordered, RTCDataChannel uses SCTP instead.
- pthatcherg 10y ago
  You can receive data messages our of order. That's all there is to it. If you could receive TCP out of order, you could just use TCP.
  - gravypod 10y ago
    Is there a way to specifiy ordering on specific packet types?
    - oneweekwonder 10y ago
      From the Article: Because SCTP is configurable, we can open multiple data channels with different settings, which saves us tons of work! Typically we have: an unreliable and unordered data channel for game state data and user inputs a reliable and ordered data channel for chat messages, scores and deaths
- manquer 10y ago
  Also WebRTC is inherently p2p . So you can connect directly to the other peer without server getting involved expect for connection (STUN and TURN). Basically message via the LAN even. Latency improves in many scenarios.
  - banachtarski 10y ago
    Latency has very little to do with the p2p aspect. In a client-server setting, the use of RTP/SCTP to communicate payloads between two clients would have significantly less latency than, say, a P2P TCP connection.
saurik 10y ago
> I'm glad you got this to work :). Matheus28: Did you actually get it to work or did you give up? (pthathcerg: The comment only claims they "analyzed the possibility".)
- Matheus28 10y ago
  I've played with a few simple examples but didn't integrate it into any games, see https://news.ycombinator.com/item?id=13267248 https://news.ycombinator.com/item?id=13267248
Matheus28 10y ago
Hey, I think you misread my comment, I haven't actually implemented it into any of my games. I've played with it for a bit but haven't gotten around actually adding it to any games. Sorry! But yeah, I really hope it becomes easier to integrate, as right now that's the biggest barrier into putting it into my custom written C++ server that I use for all my games. They already support UDP-only communication for desktop and mobile builds and bringing it to web would make the experience a lot better. Thank you!
- pthatcherg 10y ago
  Indeed, I misread your comment. Well, hopefully in the future how I read the comment will be correct. I don't think it would be that hard to write a data-channel-only server using BoringSSL and usrsctplib. See a comment of mine further down on the page of how you could do that. Or you can just wait until we have our code refactored :).
z3t4 10y ago
Using WebRTC for communicating game state seems like a hack. WebRTC is too complexed with many parts. I try to get into it every year or so but I don't even get the demos to work. Then compare to Websockets that are well supported and very easy to use, with fall-back libraries such as sockjs. If possible I think it would be a good idea to break up the different parts of WebRTC so that they can work independently of each other. The abstractions are also a bit leaky, as you need to know about the underlaying layer to use it. Another approach would be having a low level API witch might be easier to implement in the browser, and then count on libraries to make good abstractions.
- pjmlp 10y ago
  Everything on web development feels like an hack.
  - z3t4 10y ago
    Ive built some multiplyer real time web game prototypes using websockets with sockjs fallback and canvas 2d context. Its very fun and productive. You dont have to know opengl or tcp ip and it works everywhere, even on a 5 year old Nokia.
  - groovy2shoes 10y ago
    Oh, how I wish I could upvote this 100 times. Nay, 1000! It was already bad enough 10ish years ago when it was a comparatively small pile of hacks, and there was hope that something could be done about it. But now? It's an enormous pile of hack upon hack. Full stack engineer? More like full hack engineer! The main reason I worry about losing my job or moving to a new location is that web development jobs are a dime a dozen nowadays, while more traditional development is seeming less and less relevant. As much as I hate C++, I'll stick with it over the monstrosity that is Web 2.x. [Insert the usual complaints about shitty languages, tooling, and gazillions of frameworks / reinvented wheels here.]
    - z3t4 10y ago
      I can relate as I've been a web developer for 18 years and before that I did some qBASIC. Some aspects of web development have been stable for over ten years and feels like a foundation. Everything with computers is a "hack" though, the transistor is a hack, then everything on top of it is a hack. It's only when things get stable and has a tight abstraction things starts feeling non-hacky. But when something is stable (aka perfect) it no longer evolves and starts to get old. So you either use old stuff that worked 10 years ago and will work many years forward, or just accept that the bleeding edge technology you use today might be a bleeding mess tomorrow. One thing I like about computers and programming is that it's all created by humans. I tried go into physics and biology but once you go deep nothing really makes any sense, it's all random. With programming there's always, most of the time, reason behind design decisions.
Matthias247 10y ago
I also played with the idea of using WebRTC data channels for client server applications. From a system design perspective it looks good, since it can provide lots of concurrent flow controlled streams (like HTTP/2) with a potentially lower latency. However from the pure engineering side things don't look so great for the reasons Matheus28 already mentioned: WebRTC (even data channels only) is a big stack of massive complexity. It's not something you want to implement or understand fully on your own within a reasonable amount of time (like you could do with WebSockets). The most reasonable way to get WebRTC support seems like integrating Googles native WebRTC library. However one downside is that it's a big dependency with which a lot of people might be uncomfortable bringing in (although you say you are working on making it smaller). The other downside is that it's not only big but a native dependency, which I and other people want to avoid wherever possible in non C/C++ land. The alternative solution would be to develop a pure Go/.NET core/Java/etc. WebRTC data channel solution. However for this most of the required subcomponents are missing. Imho neither of those even support the required DTLS encryption in the (extended) standard libraries, and there are also no libraries for SCTP on top of UDP around. Therefore getting this to work is a serious effort, and anybody who approaches it must ask himself if the effort is justified or if Websockets and HTTP streaming are not good enough. For the latter one the performance might even reach WebRTC data channel performance if QUIC gets standardized and widely deployed. I think the situation might be different if WebRTC data channels would only have standardized a UDP or possibly encrypted UDP. Anybody who would have needed it could still be able to implement streams and multiplexing on top of it on server and client(JS) side. The current solution provides a nicer out of the box API, but supporting it outside of the browser is hard.
- Matheus28 10y ago
  I agree completely. I feel what is needed is an UDP version of WebSockets. That's all I wish we had.

shazow 10y ago

I've been trying to find some numbers on what kind of performance characteristics for using WebRTC unreliable datachannels (compared to the spectrum between pure UDP vs WebSockets). Do you know of any such comparisons? Or any intuition on the matter?

comboy 10y ago

Where does the low latency in WebRTC come from? Is it just packet ordering in TCP or is there something more to it?

Franciscouzo 10y ago
You can't do packet reordering on top of TCP as it is already ordered, RTCDataChannel uses SCTP instead.
pthatcherg 10y ago
You can receive data messages our of order. That's all there is to it. If you could receive TCP out of order, you could just use TCP.
- gravypod 10y ago
  Is there a way to specifiy ordering on specific packet types?
  - oneweekwonder 10y ago
    From the Article: Because SCTP is configurable, we can open multiple data channels with different settings, which saves us tons of work! Typically we have: an unreliable and unordered data channel for game state data and user inputs a reliable and ordered data channel for chat messages, scores and deaths
manquer 10y ago
Also WebRTC is inherently p2p . So you can connect directly to the other peer without server getting involved expect for connection (STUN and TURN). Basically message via the LAN even. Latency improves in many scenarios.
- banachtarski 10y ago
  Latency has very little to do with the p2p aspect. In a client-server setting, the use of RTP/SCTP to communicate payloads between two clients would have significantly less latency than, say, a P2P TCP connection.

saurik 10y ago

> I'm glad you got this to work :). Matheus28: Did you actually get it to work or did you give up? (pthathcerg: The comment only claims they "analyzed the possibility".)

Matheus28 10y ago
I've played with a few simple examples but didn't integrate it into any games, see https://news.ycombinator.com/item?id=13267248 https://news.ycombinator.com/item?id=13267248

Matheus28 10y ago

Hey, I think you misread my comment, I haven't actually implemented it into any of my games. I've played with it for a bit but haven't gotten around actually adding it to any games. Sorry! But yeah, I really hope it becomes easier to integrate, as right now that's the biggest barrier into putting it into my custom written C++ server that I use for all my games. They already support UDP-only communication for desktop and mobile builds and bringing it to web would make the experience a lot better. Thank you!

pthatcherg 10y ago
Indeed, I misread your comment. Well, hopefully in the future how I read the comment will be correct. I don't think it would be that hard to write a data-channel-only server using BoringSSL and usrsctplib. See a comment of mine further down on the page of how you could do that. Or you can just wait until we have our code refactored :).

z3t4 10y ago

Using WebRTC for communicating game state seems like a hack. WebRTC is too complexed with many parts. I try to get into it every year or so but I don't even get the demos to work. Then compare to Websockets that are well supported and very easy to use, with fall-back libraries such as sockjs. If possible I think it would be a good idea to break up the different parts of WebRTC so that they can work independently of each other. The abstractions are also a bit leaky, as you need to know about the underlaying layer to use it. Another approach would be having a low level API witch might be easier to implement in the browser, and then count on libraries to make good abstractions.

pjmlp 10y ago
Everything on web development feels like an hack.
- z3t4 10y ago
  Ive built some multiplyer real time web game prototypes using websockets with sockjs fallback and canvas 2d context. Its very fun and productive. You dont have to know opengl or tcp ip and it works everywhere, even on a 5 year old Nokia.
- groovy2shoes 10y ago
  Oh, how I wish I could upvote this 100 times. Nay, 1000! It was already bad enough 10ish years ago when it was a comparatively small pile of hacks, and there was hope that something could be done about it. But now? It's an enormous pile of hack upon hack. Full stack engineer? More like full hack engineer! The main reason I worry about losing my job or moving to a new location is that web development jobs are a dime a dozen nowadays, while more traditional development is seeming less and less relevant. As much as I hate C++, I'll stick with it over the monstrosity that is Web 2.x. [Insert the usual complaints about shitty languages, tooling, and gazillions of frameworks / reinvented wheels here.]
  - z3t4 10y ago
    I can relate as I've been a web developer for 18 years and before that I did some qBASIC. Some aspects of web development have been stable for over ten years and feels like a foundation. Everything with computers is a "hack" though, the transistor is a hack, then everything on top of it is a hack. It's only when things get stable and has a tight abstraction things starts feeling non-hacky. But when something is stable (aka perfect) it no longer evolves and starts to get old. So you either use old stuff that worked 10 years ago and will work many years forward, or just accept that the bleeding edge technology you use today might be a bleeding mess tomorrow. One thing I like about computers and programming is that it's all created by humans. I tried go into physics and biology but once you go deep nothing really makes any sense, it's all random. With programming there's always, most of the time, reason behind design decisions.

Matthias247 10y ago

I also played with the idea of using WebRTC data channels for client server applications. From a system design perspective it looks good, since it can provide lots of concurrent flow controlled streams (like HTTP/2) with a potentially lower latency. However from the pure engineering side things don't look so great for the reasons Matheus28 already mentioned: WebRTC (even data channels only) is a big stack of massive complexity. It's not something you want to implement or understand fully on your own within a reasonable amount of time (like you could do with WebSockets). The most reasonable way to get WebRTC support seems like integrating Googles native WebRTC library. However one downside is that it's a big dependency with which a lot of people might be uncomfortable bringing in (although you say you are working on making it smaller). The other downside is that it's not only big but a native dependency, which I and other people want to avoid wherever possible in non C/C++ land. The alternative solution would be to develop a pure Go/.NET core/Java/etc. WebRTC data channel solution. However for this most of the required subcomponents are missing. Imho neither of those even support the required DTLS encryption in the (extended) standard libraries, and there are also no libraries for SCTP on top of UDP around. Therefore getting this to work is a serious effort, and anybody who approaches it must ask himself if the effort is justified or if Websockets and HTTP streaming are not good enough. For the latter one the performance might even reach WebRTC data channel performance if QUIC gets standardized and widely deployed. I think the situation might be different if WebRTC data channels would only have standardized a UDP or possibly encrypted UDP. Anybody who would have needed it could still be able to implement streams and multiplexing on top of it on server and client(JS) side. The current solution provides a nicer out of the box API, but supporting it outside of the browser is hard.

Matheus28 10y ago
I agree completely. I feel what is needed is an UDP version of WebSockets. That's all I wish we had.