ondatachannel

Ondatachannel is an event handler in the WebRTC API, attached to RTCPeerConnection. It fires when a data channel is created by the remote peer or when the local peer receives an inbound data channel. This event enables an application to configure and use the incoming RTCDataChannel for bidirectional data transfer.

When the event occurs, the event object includes a channel property, which is the RTCDataChannel associated with the newly established data channel. If a local peer creates a data channel via createDataChannel on its RTCPeerConnection, the remote peer will receive an ondatachannel event for the inbound channel. Conversely, the local peer will handle its own data channel independently, while the remote side handles its ondatachannel event for the channel it created.

Usage typically involves assigning a function to the RTCPeerConnection’s ondatachannel handler. Within that handler, developers obtain the RTCDataChannel from the event and then configure its event listeners, such as onopen, onmessage, onclose, and onerror. Data can then be exchanged using the channel’s send method and by handling incoming messages on the channel’s onmessage callback. The data channel transitions through a lifecycle from opening to open, enabling reliable or unordered data transfer, depending on the channel’s configuration.

Compatibility and scope: ondatachannel is supported in major browsers that implement the WebRTC DataChannel API. It plays a central role in enabling peer-to-peer applications such as file transfer, multiplayer gaming, and real-time messaging by coordinating inbound data channels established during signaling and negotiation.