Go code used to investigate message across platforms for connecting to an address that is unavailable

network_connect_errors.go

import (
	"log"
	"net"
	"syscall"
	"time"
)

func main() {
	address := "127.0.0.1:5901"
	log.Printf("Trying address: %s...", address)
	l, err := net.DialTimeout("tcp", address, 2*time.Second)

	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
			log.Printf("ECONNREFUSED when connecting to: %s\n\t%v", address, e.Err)
		} else if e.Timeout() {
			log.Printf("Timeout connecting to: %s (check firewall rules)\n\t%v", address, e.Err)
		} else {
			log.Printf("Error when connecting to: %s\n\t%v", address, e.Err)
		}
	}

}