code: function sub (subURI, callback) {
    var PING_TIMEOUT = process.env['PING_TIMEOUT']
  
    if (!subURI) {
      callback(new Error('uri is required'))
      return
    }
    var domain = subURI.split('/')[2]
    var wss = 'wss://' + domain + '/'
  
    var Socket = new ws(wss, {
      origin: 'http://websocket.org'
    })
  
    Socket.on('open', function open () {
      debug('connected')
      Socket.send('sub ' + subURI)
  
      if (PING_TIMEOUT && parseInt(PING_TIMEOUT) && parseInt(PING_TIMEOUT) > 0 ) {
        setInterval(function() {
          debug('sending ping')
          Socket.send('ping')
        }, parseInt(PING_TIMEOUT * 1000))
      }
  
    })
  
    Socket.on('close', function close () {
      debug('disconnected')
    })
  
    Socket.on('message', function message (data, flags) {
      debug(data)
      callback(null, data)
    })
  }
docs: sub gets list of files for a given container
  
  @param {String} argv[2] url
  @callback {bin~cb} callback