internal/pkg/testing/port.go

// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
// or more contributor license agreements. Licensed under the Elastic License;
// you may not use this file except in compliance with the Elastic License.

package testing

import "net"

// FreePort finds a free port on the system.
func FreePort() (uint16, error) {
	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
	if err != nil {
		return 0, err
	}
	l, err := net.ListenTCP("tcp", addr)
	if err != nil {
		return 0, err
	}
	defer l.Close()

	return uint16(l.Addr().(*net.TCPAddr).Port), nil //nolint:gosec // disable G115
}