vmware-iso/driver-esxi: Detect VNC in cross-platform way [GH-1372]

Use VMware calls to determine ports being listened to, and determine
  free VNC port

builder/vmware/iso/driver_esx5.go

@@ -16,7 +16,6 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"syscall"
 	"time"
 )
 
@@ -150,24 +149,47 @@ func (d *ESX5Driver) HostIP() (string, error) {
 
 func (d *ESX5Driver) VNCAddress(portMin, portMax uint) (string, uint, error) {
 	var vncPort uint
-	// TODO(dougm) use esxcli network ip connection list
+
+	//Process ports ESXi is listening on to determine which are available
+	r, err := d.esxcli("network", "ip", "connection", "list")
+	if err != nil {
+		err = fmt.Errorf("Could not retrieve network information for ESXi: %v", err)
+		return "", 0, err
+	}
+
+	listenPorts := make(map[string]bool)
+	for record, err := r.read(); record != nil && err == nil; record, err = r.read() {
+		if record["State"] == "LISTEN" {
+			splitAddress := strings.Split(record["LocalAddress"], ":")
+			log.Print(splitAddress)
+			port := splitAddress[len(splitAddress)-1]
+			log.Printf("ESXi Listening on: %s", port)
+			listenPorts[port] = true
+		}
+	}
+
 	for port := portMin; port <= portMax; port++ {
+		if _, ok := listenPorts[string(port)]; ok {
+			log.Printf("Port %d in use", port)
+			continue
+		}
 		address := fmt.Sprintf("%s:%d", d.Host, port)
 		log.Printf("Trying address: %s...", address)
 		l, err := net.DialTimeout("tcp", address, 1*time.Second)
+		log.Printf("Dial complete address: %s...", address)
 
-		if err == nil {
-			log.Printf("%s in use", address)
-			l.Close()
-		} else if e, ok := err.(*net.OpError); ok {
-			if e.Err == syscall.ECONNREFUSED {
-				// then port should be available for listening
+		if err != nil {
+			if e, ok := err.(*net.OpError); ok {
+				if e.Timeout() {
+					log.Printf("Timeout connecting to: %s (check firewall rules)", address)
+				} else {
 					vncPort = port
 					break
-			} else if e.Timeout() {
-				log.Printf("Timeout connecting to: %s (check firewall rules)", address)
 				}
 			}
+		} else {
+			defer l.Close()
+		}
 	}
 
 	if vncPort == 0 {