Cancel request transfer, send response

code.coffee

express  = require 'express'

app = express.createServer()

app.put '/uploads/:fileid', (request,response) ->
    isvalid = false # ...code to determine validity of file being sent in the ServerRequest
    if isvalid
        # continue handling the upload
    else
        # the following two options are both unreliable
        response.connection.allowHalfOpen = false
        response.send 500,
             'Access-Control-Allow-Origin' : '*'
        # OR --------------------------------------------
        response.on 'finish', -> request.connection.destroy()
        response.send 500,
             'Access-Control-Allow-Origin' : '*'

app.listen(8888)

description

I'm trying to cancel an incoming ServerRequest and send back an appropriate ServerResponse.  I'm using the express framework, and coffeescript.  The code below does not work reliably, my guess is that the response is not being sent before the socket is closed, or the socket isn't closing on the response ending, even though allowHalfOpen is set to false.