mirror of
https://github.com/ValveSoftware/GameNetworkingSockets.git
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Fletcher Dunn
131 lines
7.1 KiB
Markdown
131 lines
7.1 KiB
Markdown
# GameNetworkingSockets
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[](https://github.com/ValveSoftware/GameNetworkingSockets/actions) [](https://github.com/ValveSoftware/GameNetworkingSockets/actions) [](https://github.com/ValveSoftware/GameNetworkingSockets/actions)
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GameNetworkingSockets is a basic transport layer for games. The features are:
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* Connection-oriented API (like TCP)
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* ... but message-oriented (like UDP), not stream-oriented.
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* Supports both reliable and unreliable message types
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* Messages can be larger than underlying MTU. The protocol performs
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fragmentation, reassembly, and retransmission for reliable messages.
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* A [reliability layer](src/steamnetworkingsockets/clientlib/SNP_WIRE_FORMAT.md)
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significantly more sophisticated than a basic TCP-style sliding window.
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It is based on the "ack vector" model from DCCP (RFC 4340, section 11.4)
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and Google QUIC and discussed in the context of games by
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[Glenn Fiedler](https://gafferongames.com/post/reliable_ordered_messages/).
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The basic idea is for the receiver to efficiently communicate to the sender
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the status of every packet number (whether or not a packet was received
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with that number). By remembering which segments were sent in each packet,
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the sender can deduce which segments need to be retransmitted.
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* Encryption. AES-GCM-256 per packet, [Curve25519](https://cr.yp.to/ecdh.html) for
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key exchange and cert signatures. The details for shared key derivation and
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per-packet IV are based on the [design](https://docs.google.com/document/d/1g5nIXAIkN_Y-7XJW5K45IblHd_L2f5LTaDUDwvZ5L6g/edit?usp=sharing)
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used by Google's QUIC protocol.
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* Tools for simulating packet latency/loss, and detailed stats measurement
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* Head-of-line blocking control and bandwidth sharing of multiple message
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streams ("lanes") on the same connection. You can use strict priority
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values, softer [weight values](https://en.wikipedia.org/wiki/Weighted_fair_queueing)
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that control how bandwidth is shared, or some combination of the two methods.
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See [``ISteamNetworkingSockets::ConfigureConnectionLanes``](include/steam/isteamnetworkingsockets.h).
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* IPv6 support
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* Peer-to-peer networking:
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* NAT traversal through google WebRTC's ICE implementation.
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* Plug in your own signaling service.
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* Unique "symmetric connect" mode.
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* [``ISteamNetworkingMessages``](include/steam/isteamnetworkingmessages.h) is an
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interface designed to make it easy to port UDP-based code to P2P use cases. (By
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UDP-based, we mean non-connection-oriented code, where each time you send a
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packet, you specify the recipient's address.)
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* See [README_P2P.md](README_P2P.md) for more info
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* Cross platform. This library has shipped on consoles, mobile platforms, and non-Steam
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stores, and has been used to facilitate cross-platform connectivity. Contact us to get
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access to the code. (We are not allowed to distribute it here.)
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What it does *not* do:
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* Higher level serialization of entities, delta encoding of changed state
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variables, etc
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* Compression
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## Quick API overview
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To get an idea of what the API is like, here are a few things to check out:
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* The [include/steam](include/steam) folder has the public API headers.
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* [``ISteamNetworkingSockets``](include/steam/isteamnetworkingsockets.h) is the
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most important interface.
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* [``steamnetworkingtypes.h``](include/steam/steamnetworkingtypes.h) has misc
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types and declarations.
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* The
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[Steamworks SDK documentation](https://partner.steamgames.com/doc/api/ISteamNetworkingSockets)
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offers web-based documentation for these APIs. Note that some features
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are only available on Steam, such as Steam's authentication service,
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signaling service, and the SDR relay service.
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* Look at these examples:
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* [example_chat.cpp](examples/example_chat.cpp). Very simple client/server
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program using all reliable messages over ordinary IPv4.
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* [test_p2p.cpp](tests/test_p2p.cpp). Shows how to get two hosts to connect
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to each other using P2P connectivity. Also an example of how to write a
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signaling service plugin.
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## Building
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See [BUILDING](BUILDING.md) for more information.
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## Language bindings
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The library was written in C++, but there is also a plain C interface
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to facilitate binding to other languages.
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Third party language bindings:
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* C#:
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* <https://github.com/nxrighthere/ValveSockets-CSharp>
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* <https://github.com/Facepunch/Facepunch.Steamworks>
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* Go:
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* <https://github.com/nielsAD/gns/>
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* Rust:
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* <https://github.com/hussein-aitlahcen/gns-rs>
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## Why do I see "Steam" everywhere?
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The main interface class is named SteamNetworkingSockets, and many files have
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"steam" in their name. But *Steam is not needed*. If you don't make games or
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aren't on Steam, feel free to use this code for whatever purpose you want.
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The reason for "Steam" in the names is that this provides a subset of the
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functionality of the [API](https://partner.steamgames.com/doc/api/ISteamNetworkingSockets)
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with the same name in the Steamworks SDK. Our main
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reason for releasing this code is so that developers won't have any hesitation
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coding to the API in the Steamworks SDK. On Steam, you will link against the
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Steamworks version, and you can access the additional services provided by
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the [Steam Datagram Relay](https://partner.steamgames.com/doc/features/multiplayer/steamdatagramrelay)
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network. On other platforms and stores, as long as you ship a version of your
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game on Steam, you might be able to take advantage of these services. See
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the Steamworks documentation for more information. Because this is a live
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service, and we need to control our security and backward compatibility burden,
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at this time we are not able to offer access to SDR on other platforms to all
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partners.
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If you aren't a Steam partner, or don't have a version of your game on Steam,
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then use this opensource version of the API and take advantage of the permissive
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license to do whatever you want. We want you to take maximum advantage of the
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features in the Steamworks version. That won't happen if this API is a weird
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"wart" that's hidden behind `#ifdef STEAM`, which is why we're making this
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opensource version available.
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The desire to match the Steamworks SDK also explains a somewhat anachronistic
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coding style and weird directory layout. This project is kept in sync with the
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Steam code here at Valve. When we extracted the code from the much larger
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codebase, we had to do some relatively gross hackery. The files in folders
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named `tier0`, `tier1`, `vstdlib`, `common`, etc have especially suffered
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trauma. Also if you see code that appears to have unnecessary layers of
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abstraction, it's probably because those layers are needed to support relayed
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connection types or some part of the Steamworks SDK.
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## Security
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Did you find a security vulnerability? Please inform us responsibly; you may
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be eligible for a bug bounty. See the [security policy](SECURITY.md) for more
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information.
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