golang/pkg/net/net.go

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net

import (
	"errors"
	"net"
)

// GetLocalIP returns local ipv4 addr from the OS.
func GetLocalIP() (string, error) {
	adds, err := net.InterfaceAddrs()
	if err != nil {
		return "", err
	}
	for _, address := range adds {
		if ip, ok := address.(*net.IPNet); ok && !ip.IP.IsLoopback() {
			if ip.IP.To4() != nil {
				return ip.IP.String(), nil
			}
		}
	}
	return "", errors.New("invalid ip address")
}

// GetFreePort returns a free port from the OS.
func GetFreePort() (int, 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 l.Addr().(*net.TCPAddr).Port, nil
}