GameNetworkingSockets

To successfully implement P2P connections using this library, you must provide or integrate the following infrastructure:

1. Signaling Service: A side channel to exchange rendezvous messages (see Signaling Service).
2. STUN Server(s): Used to help peers discover their public IP addresses and navigate firewalls.
3. Relay Fallback (TURN): If NAT piercing fails, traffic must be relayed via TURN servers. Note that TURN servers also function as STUN servers.
4. Identity & Matchmaking: A system to assign identities to hosts, authenticate them, and facilitate matchmaking (this is external to the transport library).

To use peer-to-peer (P2P) connections with ICE (Interactive Connectivity Establishment) for NAT traversal, ensure ICE is enabled during your build. It is enabled by default, but can be explicitly configured via vcpkg or CMake.

To use the native ICE client implementation (default):

• Use the vcpkg feature ice.
• Or use the CMake flag -DENABLE_ICE=ON.

To use the Google WebRTC ICE implementation instead of the native one:

• Use the CMake flag -DUSE_STEAMWEBRTC=ON. This will automatically pull down the required Google WebRTC git submodules.

While the library is written in C++, it provides a plain C interface to facilitate bindings. Third-party bindings are available for several languages:

• C#: ValveSockets-CSharp or Facepunch.Steamworks
• Go: gns
• Rust: gns-rs

Use Homebrew to install the required OpenSSL and Protobuf dependencies.

OpenSSL

GameNetworkingSockets requires OpenSSL 1.1 or later. If you encounter the error Dependency libcrypto found: NO, you must force the installation of version 1.1.

Standard installation:

brew install openssl
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/opt/openssl/lib/pkgconfig

If version 1.1 is required:

brew install openssl@1.1
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/opt/openssl@1.1/lib/pkgconfig

Protobuf

brew install protobuf

The ed25519-donna library provides performant, constant-time implementations of the Ed25519 Elliptic Curve Digital Signature Algorithm.

To use the library, include ed25519.h and link against the compiled object file (e.g., ed25519.o). If using OpenSSL, you must also link against -lssl -lcrypto.

#include "ed25519.h"

// Generate a private key
ed25519_secret_key sk;
randombytes(sk, sizeof(ed25519_secret_key));

// Generate a public key
ed25519_public_key pk;
ed25519_publickey(sk, pk);

// Sign a message
ed25519_signature sig;
ed25519_sign(message, message_len, sk, pk, signature);

// Verify a signature
int valid = ed25519_sign_open(message, message_len, pk, signature) == 0;

When running the fuzzer, successful passes result in occasional status dots and a 64-bit progress count (displayed every 0x20000 passes).

Example successful output:

fuzzing:  ref10 curved25519 curved25519-sse2

................................ [0000000000020000]
................................ [0000000000040000]

Handling Errors: If an implementation disagrees with the ref10 implementation, the program will dump:

1. The random data used (sk for Secret Key, m for Message).
2. The data generated by the ref10 implementation (pk for Public Key, sig for Signature, and valid status).
3. Diffs of the ed25519-donna data against the ref10 data.

The curve25519-donna implementation provides performant, portable 32-bit and 64-bit implementations of the Curve25519 elliptic curve. All implementations are constant-time regarding secret data. No configuration is required before compilation.

To use named versions (e.g., to avoid symbol collisions), define CURVE25519_SUFFIX during compilation. For example, using -DCURVE25519_SUFFIX=_sse2 will result in functions like curve25519_donna_sse2.

##### 32-bit
gcc curve25519.c -m32 -O3 -c

##### 64-bit
gcc curve25519.c -m64 -O3 -c

##### SSE2
gcc curve25519.c -m32 -O3 -c -DCURVE25519_SSE2 -msse2
gcc curve25519.c -m64 -O3 -c -DCURVE25519_SSE2