event handler sendHandler can not be triggered sometimes

[wshu001]

The following send function register event handler this.on('data', sendHandler) too later, sometimes if telnet server send response quickly enough, sendHandler will not be triggered because the response come in before event handler registered, , causing high lever locked if we use waitfor parameter. I have attached a fix for this issue, the fix works perfect in my testing.

index.zip

send(data, opts, callback) {
if (opts && opts instanceof Function) callback = opts

return new Promise((resolve, reject) => {
  if (opts && opts instanceof Object) {
    this.ors = opts.ors || this.ors
    this.sendTimeout = opts.timeout || this.sendTimeout
    this.maxBufferLength = opts.maxBufferLength || this.maxBufferLength
    this.waitfor = (opts.waitfor ? (opts.waitfor instanceof RegExp ? opts.waitfor : RegExp(opts.waitfor)) : false);
  }

  data += this.ors

  if (this.socket.writable) {
    this.socket.write(data, () => {
      let response = ''
      this.state = 'standby'

      this.on('data', sendHandler)

      if (!this.waitfor || !opts) {
        setTimeout(() => {
          if (response === '') {
              this.removeListener('data', sendHandler)
              reject(new Error('response not received'))
              return
          }

          this.removeListener('data', sendHandler)
          resolve(response)
        }, this.sendTimeout)
      }

      const self = this

      function sendHandler(data) {
        response += data.toString()

        if (self.waitfor) {
          if (!self.waitfor.test(response)) return

          self.removeListener('data', sendHandler)
          resolve(response)
        }
      }
    })
  } else {
    reject(new Error('socket not writable'))
  }

}).asCallback(callback)

}

[mkozjak]

@wshu001 maybe you have a PR tackling this issue?