dcs-httpd

A minimal HTTP server that can run within the DCS: World Mission Scripting environment. The server supports HTTP/1.1 GET requests with query strings and can reload the URL handlers while the mission is running.

Security Considerations

While I have tried to make the server secure, I do not claim to fully understand the Lua scripting environment inside DCS: World.

Editing your MissionScripting.lua file can possibly allow mission scripts to delete your files, send spam and kill your cat. Use this at your own risk.

Initial Setup

• Copy the files to %USERPROFILE%\Saved Games\DCS\Scripts\dcs-httpd (e.g. C:\Users\<Your Username>\Saved Games\DCS\Scripts\dcs-httpd).
• Go to your DCS: World installation directory (most likely C:\Program Files\Eagle Dynamics\DCS World), open the Scripts subfolder and edit the file MissionScripting.lua. Add the following code somewhere before the function sanitizeModule is defined:

httpd = {}
-- uncomment the following lines and change the paths
-- if you want the server to look elsewhere for files and URL handlers
-- httpd.document_root = lfs.writedir()..[[Scripts\dcs-httpd\public_html\]]
-- httpd.handlerdir = lfs.writedir()..[[Scripts\dcs-httpd\url_handlers\]]
httpd.bind_address = "localhost" -- set to "*" to allow connections from other computers
dofile(lfs.writedir()..[[Scripts\dcs-httpd\httpd.lua]])

Adding the HTTP server to a mission

To start the server, your mission will have to call httpd.start(timer, env) (you have to pass it the timer and env objects because they are not available at the point the server is defined).

Simply create a new trigger set to fire ONCE, create a new condition TIME IS MORE (1 second) and create a DO SCRIPT action with the text httpd.start(timer, env).

Then start your mission, enter a slot (or unpause it in multiplayer) and point your browser at http://localhost:12080 and it should tell you its version. You can also try http://localhost:12080/example.html to get a static HTML file.

URL handlers

The object httpd.url_handlers maps regular expressions to URL handler functions. The first function whose regex matches the request URL will handle it. If no handler function is found, the server will look for a static file under the directory httpd.document_root instead (that variable is only read once during initialization).

Look at the file url_handlers\example.lua to see how to write your own handlers.

On startup, all lua files in the url_handlers directory are executed. When you browse to http://localhost:12080/reload/, they will be re-read.

Note: The /reload/ URL is a special case and cannot be overridden in a custom URL handler.

Debugging with dcs-httpd

The URL handlers you write are executed in the same context as your mission scripts. During a running mission, you can simply Alt+Tab out of the game, edit your URL handler, browse to the /reload/ URL to reload it, and then browse to its URL to execute the code.

It probably gets even more convenient if you have a second computer handy and put the URL handlers in a shared folder. Make sure to set httpd.bind_address to "*" in MissionScripting.lua to listen to requests from other computers.

License

The code is released under the terms of the GNU GPLv3 or any later version (see the LICENSE file).