Report a more friendly error message on WSAEACCES

cli/main.go

@@ -2,13 +2,28 @@ package main
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"strings"
+	"syscall"
 
 	"github.com/spf13/cobra"
 	"golang.org/x/exp/slog"
 )
 
+const (
+	// WSAEACCES is the Windows error code for attempting to access a socket that you don't have permission to access.
+	//
+	// This commonly occurs if the socket is in use or was not closed correctly, and can be resolved by restarting the hns service.
+	WSAEACCES = 10013
+)
+
+// IsWindowsPortAccessError determines if the given error is the error WSAEACCES.
+func IsWindowsPortAccessError(err error) bool {
+	var syscallErr *syscall.Errno
+	return errors.As(err, &syscallErr) && *syscallErr == WSAEACCES
+}
+
 func init() {
 	var opts slog.HandlerOptions
 	if os.Getenv("DEBUG") == "1" {
@@ -27,6 +42,12 @@ func main() {
 	rootCmd.SetArgs(args)
 
 	err := rootCmd.Execute()
+	if IsWindowsPortAccessError(err) {
+		fmt.Fprintf(os.Stderr, "Encountered an issue when opening the port for KeyConjurer: %s\n", err)
+		fmt.Fprintln(os.Stderr, "Consider running `net stop hns` and then `net start hns`")
+		os.Exit(ExitCodeConnectivityError)
+	}
+
 	var codeErr codeError
 	if errors.As(err, &codeErr) {
 		cobra.CheckErr(codeErr)