nats-io/nats-server · error

can't specify both HTTP (%v) and HTTPs (%v) ports

Error message

can't specify both HTTP (%v) and HTTPs (%v) ports

What it means

StartMonitoring rejects configs that set both the plain HTTP monitoring port and the HTTPS monitoring port; only one monitor listener may be configured. The message includes both conflicting port values.

Source

Thrown at server/server.go:3029

// DEPRECATED: Should use StartMonitoring.
func (s *Server) StartHTTPMonitoring() {
	s.startMonitoring(false)
}

// StartHTTPSMonitoring will enable the HTTPS monitoring port.
// DEPRECATED: Should use StartMonitoring.
func (s *Server) StartHTTPSMonitoring() {
	s.startMonitoring(true)
}

// StartMonitoring starts the HTTP or HTTPs server if needed.
func (s *Server) StartMonitoring() error {
	// Snapshot server options.
	opts := s.getOpts()

	// Specifying both HTTP and HTTPS ports is a misconfiguration
	if opts.HTTPPort != 0 && opts.HTTPSPort != 0 {
		return fmt.Errorf("can't specify both HTTP (%v) and HTTPs (%v) ports", opts.HTTPPort, opts.HTTPSPort)
	}
	var err error
	if opts.HTTPPort != 0 {
		err = s.startMonitoring(false)
	} else if opts.HTTPSPort != 0 {
		if opts.TLSConfig == nil {
			return fmt.Errorf("TLS cert and key required for HTTPS")
		}
		err = s.startMonitoring(true)
	}
	return err
}

// HTTP endpoints
const (
	RootPath         = "/"
	VarzPath         = "/varz"
	ConnzPath        = "/connz"

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Keep only one: delete `http_port` if you want TLS monitoring, or delete `https_port` for plain HTTP
2. Check the effective merged config (`nats-server --signal reload` logs, or start with -V) for both keys
3. Audit systemd/CLI flags for a duplicate -m/--https_port

Example fix

// before
http_port: 8222
https_port: 8223
// after
https_port: 8223
tls { cert: "server.pem", key: "server-key.pem" }

// Reject double monitoring ports before server start
if cfg.HTTPPort != 0 && cfg.HTTPSPort != 0 {
    return errors.New("configure only one of http_port or https_port for monitoring")
}

When it happens

Trigger: Options contain both opts.HTTPPort != 0 and opts.HTTPSPort != 0, e.g. config with both `http_port: 8222` and `https_port: 8223`, or flags `-m 8222 --https_port 8223` combined.

Common situations: Merging two config files (one with http_port, one with https_port); flag-based overrides stacking on a config that already sets the other port; environment/templating filling both values.

Related errors

• TLS cert and key required for HTTPS
• failed to create mapping transform for stream import subject
• store operation not supported for URL Resolver
• delete must be enabled in server config
• Fetch timeout %v is too smal

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/376e3dac7fae3232. Report an issue: GitHub.