Socket.write()

Asynchronously sends data to the remote server. Returns a Promise that resolves when the data has been written to the socket.

Signature

socket.write(data, options)

Parameters

Parameter	Type	Description
data	string \| ArrayBuffer	Data to send. Use `ArrayBuffer` for binary data
options	object	Optional write configuration
options.encoding	string	Encoding for string data: `utf8` / `utf-8` (default), `ascii`, `base64`, `base64url`, `hex`. Ignored when `data` is an `ArrayBuffer`
options.tags	object	Custom tags for this write operation’s metrics (key-value pairs)

Returns

Type	Description
Promise<void>	Resolves when the data has been written to the socket

Example

import { Socket } from "k6/x/tcp"

export default async function () {
  const socket = new Socket()
  const closed = new Promise((resolve) => { socket.on("close", resolve) })
  socket.on("error", (err) => { console.error("Error:", err) })

  await socket.connect(8080, "example.com")

  // Write a plain text string (utf8 by default)
  await socket.write("Hello, server!")

  // Write base64-encoded data
  await socket.write("SGVsbG8gV29ybGQ=", { encoding: "base64" })

  // Write with custom tags for metrics
  await socket.write("request payload", {
    tags: { operation: "auth-request" },
  })

  socket.destroy()
  await closed
}