nodemcu-httpserver

A (very) simple web server written in Lua for the ESP8266 firmware NodeMCU.

Features

• GET
• Multiple MIME types
• Error pages (404 and others)
• Server-side execution of Lua scripts
• Query string argument parsing

How to use

1. Upload server files using nodemcu-uploader or similar. Or, even better, use GNU Make with the bundled makefile. Type the following to upload server code, init.lua (which you may want to modify), and some example files:

     make upload
   

   If you only want to upload the server code, then type:

     make upload_server
   

   And if you only want to upload the http files:

     make upload_http
   

   Restart the server. This will execute init.lua which will compile the server code. Then, assuming init.lua doesn't have it, start the server yourself by typing:

     dofile("httpserver.lc")(80)
   

   In this example, 80 is the port your server is listening at but you can change it.

2. Want to upload your own files? Move them to the http/ folder. Be careful though, the flash memory seems to fill up quickly and get corrupted.

   All the files you upload must be prefixed with "http/". Wait, what?

   Yes: NodeMCU's filesystem does not support folders, but filenames can contain slashes. Only files that begin with "http/" will be accessible through the server.

3. Visit your server from a web browser.

   Example: Say the IP for your ESP8266 is 2.2.2.2 and the server is running in the default port 80. Go to (http://2.2.2.2/index.html)[http://2.2.2.2/index.html] using your web browser. The ESP8266 will serve you with the contents of the file "http/index.html" (if it exists). If you visit the root (/) then index.html is served. By the way, unlike most HTTP servers, nodemcu_httpserver treats the URLs in a case-sensitive manner.

How to create dynamic Lua scripts

Similar to static files, upload a Lua script called "http/[name].lua where you replace [name] with your script's name. The script should return a function that takes two parameters:

  return function (connection, args)
     -- code goes here
  end

Use the connection parameter to send the response back to the client. Note that you are in charge of sending the HTTP header. The args parameter is a Lua table that contains any arguments sent by the client in the GET request.

For example, if the client requests http://2.2.2.2/foo.lua?color=red then the server will execute the function in your Lua script foo.lua and pass in connection and args, where args.color == "red".

If you are going to be sending lots (as in over a KB) of data, you should yield the thread/coroutine every now and then in order to avoid overflowing the buffer in the microcontroller. Use:

  coroutine.yield()

The easiest is to check out the included example scripts for more ideas.

Example: Garage door opener

Purpose

This is a bundled example that shows how to use nodemcu-httpserver together with server-side scripting to control something with the ESP8266. In this example, we will pretend to open a garage door. This is a very simple example that doesn't even use arguments passed in the request (see example args.lua for that).

Your typical garage door opener has a wired remote with a single button. The button simply connects to two terminals on the electric motor and when pushed, the terminals are shorted. This causes the motor to open or close.

Hardware description

This example assumes that GPIO2 on the ESP8266 is connected to a relay that can be controlled. How to wire such thing is outside of the scope of this document [but information is easily found online] (https://www.google.com/search?q=opening+a+garage+door+with+a+microcontroller). The relay is controlled by the microcontroller and acts as the button, and can actually be connected in parallel with the existing mechanical button.

Software description

This example consists of the following files:

• garage_door_opener.html: Static HTML displays a button with a link to the garage_door_opener.lua script. That's it!
• garage_door_opener.css: Provides styling for garage_door_opener.html just so it looks pretty.
• garage_door_opener.lua: Does the actual work. The script first sends a little javascript snippet to redirect the client back to garage_door_opener.html and then toggles the GPIO2 line for a short amount of time (roughly equivalent to the typical button press for opening a garage door) and then toggles it back.
• apple-touch-icon.png: This is optional. Provides an icon that will be used if you "Add to Home Screen" the demo. Now it looks like an app!`

Security implications

Be careful permanently installing something like this in your home. The scripts use no authentication and no encryption. Your only layer of security is your wifi network and anyone with access to it could open or close your garage, enter your home, and steal your flatscreen TV.

This script is provided simply as an educational example and you should treat accordingly.

Not supported

• Other methods: HEAD, POST, PUT, DELETE, TRACE, OPTIONS, CONNECT, PATCH
• HTTP authentication
• Encryption

Notes on memory usage.

The chip is very, very memory constrained. You must use a build of nodemcu-firmware recent enough to support node.compile() since the server expects all server scripts to be compiled.

• It is recommended you use a firmware build without support for floating point. In the (nodemcu-firmware releases page)[https://github.com/nodemcu/nodemcu-firmware/releases] these would be the ones with the term "integer" in them. If you want to build your own, then edit file app/include/user_config.h right around line 58 (line number may change) by uncommenting

  #define LUA_NUMBER_INTEGRAL
  

  Then rebuild and re-flash the firmware.

• Any help reducing the memory needs of the server without crippling its features are appreciated!

• You can compile your Lua scripts in order to reduce their memory usage. The server knows to treat both .lua and .lc files as scripts.