Running a node.js REPL over `curl`

bbs.js

/**
 * Requires node v0.7.7 or greater.
 *
 * To connect: $ curl -sSNT. localhost:8000
 */

var http = require('http')
  , repl = require('repl')
  , buf0 = new Buffer([0])

var server = http.createServer(function (req, res) {
  res.setHeader('content-type', 'multipart/octet-stream')

  res.write('Welcome to the Fun House\r\n')
  repl.start({
      prompt: 'curl repl> '
    , input: req
    , output: res
    , terminal: false
    , useColors: true
    , useGlobal: false
  })

  // log
  console.log(req.headers['user-agent'])

  // hack to thread stdin and stdout
  // simultaneously in curl's single thread
  var iv = setInterval(function () {
    res.write(buf0)
  }, 100)

  res.connection.on('end', function () {
    clearInterval(iv)
  })
})
server.listen(8000)

output

☮ ~ (master) ⚡ curl -sSNT. localhost:8000
Welcome to the Fun House
curl repl> process.platform
'darwin'
curl repl> process.arch
'x64'
curl repl> process.cwd()
'/Users/nrajlich'
curl repl> path
{ resolve: [Function],
  normalize: [Function],
  join: [Function],
  relative: [Function],
  dirname: [Function],
  basename: [Function],
  extname: [Function],
  _makeLong: [Function] }
curl repl> ^C
☮ ~ (master) ⚡ 

nginx will ensure it will behave itself, as in, it will strictly speak standard HTTP to your web app. This is a protective feature. The idea in this thread uses a non-standard protocol and disguises it as HTTP, very thinly. The disguise breaks as soon as you insert a component that expects real HTTP.

Edit: You might get away with HTTP UPGRADE somehow, but it will probably be a bit more complicated.

Do you have any idea about how to UPGRADE it?

On Ubuntu 20.04, curl takes a lot of CPU resources (more then 25%) to run this example.