main.go

package main

import (
    "bufio"
    "fmt"
    "net"
    "os"
    "sync"
    "time"
    "io"
)

const (
    timeout = 10
    port    = "5900"
)

func test(addr string, results chan<- string, wg *sync.WaitGroup) {
    wg.Add(1)
    defer wg.Done()

    deadline := time.Now().Add(time.Duration(timeout) * time.Second)
    dialer := net.Dialer{Deadline: deadline}
    conn, err := dialer.Dial("tcp", net.JoinHostPort(addr, port))

    if err != nil {
        return
    }

    conn.SetReadDeadline(deadline)
    conn.SetWriteDeadline(deadline)
    var version [1024]byte
    var auth [1024]byte

    n, err := conn.Read(version[:])
    if err != nil && (err != io.EOF || n == 0) {
        fmt.Fprintln(os.Stderr, err.Error())
        return
    }

    n, err = conn.Write(version[:])
    if err != nil {
        fmt.Fprintln(os.Stderr, err.Error())
        return
    }

    n, err = conn.Read(auth[:])
    if err != nil && (err != io.EOF || n == 0) {
        fmt.Fprintln(os.Stderr, err.Error())
        return
    }
    conn.Close()

    // interpret vnc auth packet, accept it if one
    // of the methods it supports is "unauthenticated"
    for i := 0; i < int(auth[0]); i++ {
        if auth[i+1] == 1 {
            results <- addr
        }
    }

    return
}

func main() {
    scanner := bufio.NewScanner(os.Stdin)
    resultsChan := make(chan string)
    var wg sync.WaitGroup

    go func() {
        for ip := range resultsChan {
            fmt.Println(ip)
        }
    }()

    for scanner.Scan() {
        go test(scanner.Text(), resultsChan, &wg)
    }

    close(resultsChan)
    wg.Wait()
}