example_test.go

// Copyright 2017 Mikio Hara. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tcp_test

import (
	"crypto/tls"
	"encoding/json"
	"fmt"
	"log"
	"net"
	"net/http"

	"github.com/mikioh/tcp"
	"github.com/mikioh/tcpinfo"
	"github.com/mikioh/tcpopt"
)

// Monitoring a TCP connection
//
// For now only Darwin, FreeBSD, Linux and NetBSD kernels support the
// TCP information option. A custom net.Dial function that hooks up an
// underlying transport connection must be prepared before monitoring.
func ExampleConn() {
	// When the underlying transport connection is established,
	// your monitor goroutine can start monitoring the connection
	// by using the Option method of Conn and tcpinfo package.
	monitor := func(tc *tcp.Conn) {
		tc.SetOption(tcpopt.KeepAlive(true))
		tc.SetOption(tcpopt.KeepAliveProbeCount(3))
		var o tcpinfo.Info
		var b [256]byte
		for {
			i, err := tc.Option(o.Level(), o.Name(), b[:])
			if err != nil {
				log.Println(err)
				return
			}
			txt, err := json.Marshal(i)
			if err != nil {
				log.Println(err)
				return
			}
			fmt.Println(string(txt))
		}
	}

	tr := &http.Transport{
		Dial: func(network, address string) (net.Conn, error) {
			d := net.Dialer{DualStack: true}
			c, err := d.Dial(network, address)
			if err != nil {
				return nil, err
			}
			tc, err := tcp.NewConn(c)
			if err != nil {
				c.Close()
				return nil, err
			}
			go monitor(tc)
			return tc.Conn, nil
		},
		TLSClientConfig: &tls.Config{ServerName: "golang.org"},
	}
	client := http.Client{Transport: tr}
	resp, err := client.Get("https://golang.org")
	if err != nil {
		log.Fatal(err)
	}
	resp.Body.Close()
}