aiortc-native-sctp

Native usrsctp SCTP transport for aiortc RTCDataChannel.

The package leaves aiortc's RTCPeerConnection, DCEP, DTLS and ICE paths in place and replaces aiortc's pure-Python SCTP transport with a small CPython extension backed by usrsctp.

Current source is built around:

• aiortc 1.15.0
• usrsctp 0.9.5.0
• SCTP MTU 1200
• 4 MiB send / receive buffers
• delayed SACK frequency 2, 20 ms
• 10 ms userspace timer tick

Use

Install the wheel, then install the replacement before creating any RTCPeerConnection:

from aiortc_native_sctp import install_native_sctp

install_native_sctp()

from aiortc import RTCPeerConnection

Existing aiortc application code does not otherwise need to change.

Windows build

Requirements:

• Python development environment
• Visual Studio C++ Build Tools
• CMake
• Git

From a normal PowerShell in this repository:

.\build-windows.ps1

The script:

1. clones usrsctp 0.9.5.0 into .build\usrsctp-src if needed;
2. builds a static usrsctp library into .build\usrsctp-install;
3. builds aiortc_native_sctp as a wheel into dist\;
4. installs that wheel into the current Python environment;
5. runs the loopback native SCTP smoke test.

To use an existing usrsctp source tree instead:

.\build-windows.ps1 -UsrsctpSource C:\path\to\usrsctp

Linux build

Requirements:

• Python development environment
• C/C++ build tools
• CMake
• Git

From this repository:

./build-linux.sh

To select a Python interpreter:

PYTHON=python3.12 ./build-linux.sh

To use an existing usrsctp source tree:

./build-linux.sh /path/to/usrsctp

Everything is built under .build/; the wheel is written to dist/, then installed into the selected Python environment and smoke-tested.

macOS build

Requirements:

• Python development environment
• Xcode Command Line Tools
• CMake
• Git

From this repository:

./build-macos.sh

The script builds for the current machine architecture (arm64 or x86_64). You can override the interpreter or architecture when needed:

PYTHON=python3.12 ./build-macos.sh
ARCH=arm64 ./build-macos.sh

To use an existing usrsctp source tree:

./build-macos.sh /path/to/usrsctp

If MACOSX_DEPLOYMENT_TARGET is already set, the same target is passed to the usrsctp CMake build and the Python wheel build environment.

Build manually

If usrsctp is already installed somewhere:

$env:USRSCTP_ROOT = "C:\path\to\usrsctp-install"
python -m pip install build
python -m build --wheel

The wheel is written to dist\.

GitHub / requirements.txt

A Git VCS dependency builds from source, so it still needs a local usrsctp build and USRSCTP_ROOT:

aiortc-native-sctp @ git+https://github.com/nuwainfo/aiortc-native-sctp.git@main

For machines where you do not want to compile usrsctp, upload your prebuilt wheel to a GitHub Release and point requirements.txt directly at that wheel, for example:

aiortc-native-sctp @ https://github.com/nuwainfo/aiortc-native-sctp/releases/download/v0.1.0/aiortc_native_sctp-0.1.0-cp312-cp312-win_amd64.whl ; sys_platform == "win32" and python_version == "3.12"

Smoke test

After installation:

python -m aiortc_native_sctp.smoke

The smoke test creates two in-process AF_CONN associations, transfers a 256 KiB message and verifies its stream id, PPID and contents.

Notes

usrsctp is not vendored in this repository. The Windows build script fetches the 0.9.5.0 source tree when needed. If you publish statically linked wheels, retain the upstream usrsctp license and notices with your distribution.