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Socket.connect()

Asynchronously establishes a TCP connection to a remote server. Returns a Promise that resolves when the connection is established, or rejects on failure.

Signature

JavaScript 
// Overload 1: port and optional host
socket.connect(port, host)

// Overload 2: options object
socket.connect(options)

Parameters

Overload 1

ParameterTypeDescription
portnumber | stringDestination port (1-65535)
hoststringDestination hostname or IP address. Defaults to 'localhost'

Overload 2

ParameterTypeDescription
options.portnumber | stringDestination port (required)
options.hoststringDestination hostname or IP address. Defaults to 'localhost'
options.tlsbooleanEnable TLS/SSL encryption. Defaults to false
options.tagsobjectCustom tags for connection metrics (key-value pairs)

Returns

TypeDescription
Promise<void>Resolves when the connection is established. Rejects on connection failure

TLS/SSL configuration

When tls: true is set, the socket performs a TLS handshake after establishing the TCP connection. TLS settings such as certificates, verification, and cipher suites are controlled by k6’s standard TLS configuration.

Example

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

export default async function () {
  // Overload 1: connect with separate port and host
  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")
  console.log("Connected")
  socket.destroy()
  await closed

  // Overload 2: connect with options object and TLS
  const tlsSocket = new Socket({ tags: { protocol: "tls" } })
  const tlsClosed = new Promise((resolve) => { tlsSocket.on("close", resolve) })
  tlsSocket.on("error", (err) => { console.error("TLS error:", err) })

  await tlsSocket.connect({
    port: 443,
    host: "secure.example.com",
    tls: true,
  })
  console.log("TLS connection established")
  tlsSocket.destroy()
  await tlsClosed
}