Go script for testing your internet connection (by downloading an large file and verifying that it continues to download).

networkTest.go

package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"time"
)

const BLOCK_SIZE = 4096
const MAX_PAUSE = 30 * time.Second

func monitor(body io.Reader, c chan int) {
	bytes := make([]byte, BLOCK_SIZE)
	for {
		if _, err := body.Read(bytes); err != nil {
			c <- 0
			break
		} else {
			c <- 1
		}
	}
}

func delay(tick time.Time) time.Duration {
	return time.Now().Sub(tick)
}

func TrackDownload(url string) {
	var c = make(chan int)
	tick := time.Now()
	count := 0
	resp, err := http.Get(url)
	defer resp.Body.Close()
	if err != nil {
		fmt.Fprintln(os.Stderr, "reading standard input:", err)
	}
	go monitor(resp.Body, c)
	go func() {
		for {
			time.Sleep(1 * 1e9)
			c <- 2
		}
	}()
	for {
		switch <-c {
		case 0:
			fmt.Printf("Completed with: %v blocks.\n", count)
			return
		case 1:
			tick = time.Now()
			count += 1
		case 2:
			delay := delay(tick)
			fmt.Printf("Count: %v (last packet received %v ago).\n", count, delay)
			if delay > MAX_PAUSE {
				fmt.Printf("Declared dead; no update after %v.\n", delay)
				return
			}
		}
	}
}

func GetUrl() string {
	if len(os.Args) < 2 {
		fmt.Printf("Used to track when a connection drops for HTTP downloads\n\n")
		fmt.Printf("Usage:\n\t%v URL\n", os.Args[0])
		fmt.Printf("Example:\n\t%v \"http://releases.ubuntu.com//precise/ubuntu-12.04.2-desktop-amd64.iso\"\n", os.Args[0])
		os.Exit(1)
	}
	return os.Args[1]
}

func main() {
	TrackDownload(GetUrl())
}