doc: about static_file plugin

README.md

@@ -20,6 +20,7 @@ frp is a fast reverse proxy to help you expose a local server behind a NAT or fi
     * [Visit your web service in LAN by custom domains](#visit-your-web-service-in-lan-by-custom-domains)
     * [Forward DNS query request](#forward-dns-query-request)
     * [Forward unix domain socket](#forward-unix-domain-socket)
+    * [Expose a simple http file server](#expose-a-simple-http-file-server)
     * [Expose your service in security](#expose-your-service-in-security)
     * [P2P Mode](#p2p-mode)
     * [Connect website through frpc's network](#connect-website-through-frpcs-network)
@@ -214,6 +215,32 @@ Configure frps same as above.
 
   `curl http://x.x.x.x:6000/version`
 
+### Expose a simple http file server
+
+A simple way to visit files in the LAN.
+
+Configure frps same as above.
+
+1. Start frpc with configurations:
+
+  ```ini
+  # frpc.ini
+  [common]
+  server_addr = x.x.x.x
+  server_port = 7000
+
+  [test_static_file]
+  type = tcp
+  remote_port = 6000
+  plugin = static_file
+  plugin_local_path = /tmp/file
+  plugin_strip_prefix = static
+  plugin_http_user = abc
+  plugin_http_passwd = abc
+  ```
+
+2. Visit `http://x.x.x.x:6000/static/` by your browser, set correct user and password, so you can see files in `/tmp/file`.
+
 ### Expose your service in security
 
 For some services, if expose them to the public network directly will be a security risk.