tcpping.go

package main

import (
	"log"
	"net"
	"os"
	"time"
)

var (
	host string
	port string
)

func init() {
	if len(os.Args) != 3 {
		log.Fatalf("usage: %s <host> <port>", os.Args[0])
	}

	host = os.Args[1]
	port = os.Args[2]
}

func main() {
	addrs, err := net.LookupHost(host)
	if err != nil {
		log.Fatalf("unable to resolve address for host %q: %s", host, err)
	}
	if len(addrs) == 0 {
		log.Fatal("no address found for host %q", host)
	}

	for {
		t := time.Now()
		conn, err := net.Dial("tcp", net.JoinHostPort(addrs[0], port))
		if err != nil {
			log.Fatalf("%s", err)
		}
		latency := time.Now().Sub(t)
		conn.Close()

		log.Printf("%s[%s]:%s\t%s\n", host, addrs[0], port, latency)

		time.Sleep(time.Second)
	}
}

Example usage:

$ go build && ./tcpping www.exoscale.com 80
2019/03/14 17:03:16 www.exoscale.com[2a04:c44:e00:147a:446:6aff:fe00:321]:80	32.062172ms
2019/03/14 17:03:17 www.exoscale.com[2a04:c44:e00:147a:446:6aff:fe00:321]:80	31.754957ms
2019/03/14 17:03:18 www.exoscale.com[2a04:c44:e00:147a:446:6aff:fe00:321]:80	31.88527ms