v142 · network / connectivity

Multicast support for Direct Sockets API

This feature allows [Isolated Web Apps](https://chromeos.dev/en/web/isolated-web-apps) (IWAs) to subscribe to multicast groups and receive User Datagram Protocol (UDP) packets from there. IWAs can now also specify additional parameters when sending UDP packets to multicast addresses.

concepts

  1. Multicast Receiver

    Pick a multicast group, join, send packets — watch the simulated network route them to subscribed receivers. Try the real UDPSocket constructor; it only succeeds inside an Isolated Web App.

  2. Service Discovery (mDNS-style)

    The use case authors keep flagging: peer service discovery on the LAN without a central rendezvous server. Joins 224.0.0.251:5353 and broadcasts a service query, simulating the printer/cast/workstation reply set.

  3. Sync Display Wall

    The motivating use case from the explainer: a shopping-mall video wall. One sender drives eight receivers over a multicast group, all rendering the same canvas animation in lock-step. Toggle packet loss to see degradation curves.

  4. Packet Sniffer Visualizer

    A network topology diagram showing a sender, two multicast groups, and six receivers. Toggle which groups each receiver joins, then broadcast packets and watch them fan out only to subscribed members. A live packet log timestamps each delivery with TTL, payload size, and group address.

why it shipped

1. Synchronous video stream from one device to the whole network of devices. For example, imagine in a shopping mall there would be multiple displays which show videos simultaneously on all devices.

references