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connect( url, params, callback )

A module with a better and standard API exists

The new k6/experimental/websockets API partially implements the WebSockets API living standard.

When possible, we recommend using the new API. It uses a global event loop for consistency with other k6 APIs and better performance.

Initiate a WebSocket connection to a remote host.

Calling connect will block the VU finalization until the WebSocket connection is closed. Instead of continuously looping the main function (export default function() { ... }) over an over, each VU will be halted listening to async events and executing their event handlers until the connection is closed.

The following events can close the connection:

  • remote host close event.
  • Socket.close().
  • k6 VU interruption based on test configuration or CLI commands.
urlstringRequest URL (e.g. "ws://").
paramsobjectParams object containing additional request parameters.
callbackfunctionThe callback function that will be called when the WebSocket connection is initiated. A Socket object will be passed to the function, and this object can be used to set up callbacks etc when things happen on the WebSocket connection


ResponseHTTP Response object.


import ws from 'k6/ws';
export default function () {
const url = 'ws://';
const resp = ws.connect(url, null, function (socket) {
socket.on('open', function () {
console.log('WebSocket connection established!');