请问出现这个是什么情况呢

F:\ngrok>ngrok 8080
NAME:
   ngrok - tunnel local ports to public URLs and inspect traffic

DESCRIPTION:
    ngrok exposes local networked services behinds NATs and firewalls to the
    public internet over a secure tunnel. Share local websites, build/test
    webhook consumers and self-host personal services.
    Detailed help for each command is available with 'ngrok help <command>'.
    Open http://localhost:4040 for ngrok's web interface to inspect traffic.

EXAMPLES:
    ngrok http 80                    # secure public URL for port 80 web server
    ngrok http -subdomain=baz 8080   # port 8080 available at baz.ngrok.io
    ngrok http foo.dev:80            # tunnel to host:port instead of localhost
    ngrok tcp 22                     # tunnel arbitrary TCP traffic to port 22
    ngrok tls -hostname=foo.com 443  # TLS traffic for foo.com to port 443
    ngrok start foo bar baz          # start tunnels from the configuration file

VERSION:
   2.1.2

AUTHOR:
  inconshreveable - <alan@ngrok.com>

COMMANDS:
   authtoken    save authtoken to configuration file
   credits      prints author and licensing information
   http         start an HTTP tunnel
   start        start tunnels by name from the configuration file
   tcp          start a TCP tunnel
   test         test ngrok service end-to-end
   tls          start a TLS tunnel
   update       update ngrok to the latest version
   version      print the version string
   help         Shows a list of commands or help for one command

ERROR:  Unrecognized command: 8080