Cacao (CORS Access-Control-Allow-Origin) Proxy

Cacao is a localhost Cross-Origin (CORS) proxy. It allows Javascript running in a web browser to access a remote HTTP resource without cross-origin restrictions. It runs on several different platforms, and essentially works by adding a Access-Control-Allow-Origin: * header to an HTTP response.

IP Camera Streaming

The main use case is to access a remote streaming MJPEG URL published by an IP Camera, via an <img> tag pointing to Cacao. Without Cacao, this image data is usually marked as cross-origin, and therefore cannot be used as the source for a WebRTC stream.

With Cacao, an <img crossorigin> can be copied to a <canvas> and then (since CORS is allowed) sent by the browser via WebRTC. Try loading the (MJPEG sample)[static/mjpeg.html] in your browser to experiment with this capability, and to understand the vanilla Javascript source code.

The Mediasoup Broadcast Example will eventually add support for using Cacao to request media to stream.

Usage

Cacao Proxy

Cacao can be run as a localhost proxy server on Linux (and other Unix-like), MacOS, and Windows.

Download a binary package from the Cacao releases, if you just want to use the proxy (and not change its code).

If you are a developer, you can run Cacao directly from sources in this project, but you will first need to install the Dart SDK:

$ dart --version
$ bin/cacao --help

Cacao Proxy App

See the Cacao Proxy App for a graphical app for controlling a builtin Cacao proxy on your mobile device.

Michael FIG michael+cacao@fig.org, 2018-12-05