WebSockets
Background
WebSockets allow you to communicate in real time with your Cloudflare Workers serverless functions.
Constructor
// { 0: <WebSocket>, 1: <WebSocket> }
let websocketPair = new WebSocketPair();
The WebSocketPair returned from this constructor is an Object, with two WebSockets at keys 0 and 1.
These WebSockets are commonly referred to as client and server. The below example combines Object.values and ES6 destructuring to retrieve the WebSockets as client and server:
let [client, server] = Object.values(new WebSocketPair());
Methods
accept
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accept()- Accepts the Websocket connection and begins terminating requests for the WebSocket at Cloudflare’s edge. This effectively enables the Workers runtime to begin responding to and handling WebSocket requests.
addEventListener
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addEventListener(eventWebSocketEvent, callbackFunctionFunction)- Add callback functions to be executed when an event has occurred on the WebSocket.
Parameters
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eventWebSocketEvent- The WebSocket event (refer to Events to listen to.
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callbackFunction(messageMessage)Function- A function to be called when the Websocket responds to a specific event.
close
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close(codenumber, reasonstring)Close the WebSocket connection.
Parameters
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codeinteger- An integer indicating the close code sent by the server. This should match an option from the list of status codes provided by the WebSocket spec.
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reasonstring- A human-readable string indicating why the WebSocket connection was closed.
send
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send(messagestring)Send a message to the other WebSocket in this WebSocket pair.
Parameters
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messagestring- The message to send down the WebSocket connection to the corresponding client. This should be a string or something coercible into a string; for example, strings and numbers will be simply cast into strings, but objects and arrays should be cast to JSON strings using
JSON.stringify, and parsed in the client.
- The message to send down the WebSocket connection to the corresponding client. This should be a string or something coercible into a string; for example, strings and numbers will be simply cast into strings, but objects and arrays should be cast to JSON strings using
Events
close
An event indicating the WebSocket has closed.
error
An event indicating there was an error with the WebSocket.
message
An event indicating a new message received from the client, including the data passed by the client.
Types
Message
dataany- The data passed back from the other WebSocket in your pair.typestring- Defaults tomessage.