promise.js

class ExtendedSocket extends Socket {
  // ...
  // need to use this to get the error response.
  tellErrorCode() {
    return new Promise((resolve, reject) => {
      this.once('data', data => {
        resolve(new Error('CommandError', data.replace(/\:\r\n/, '')));
      }).write('TC 1\r\n'); // asks for the error
    }).timeout(5000);
  }
  send(command) {
    let listener;
    return new Promise((resolve, reject) => {
      listener = data => {
        data.split(/\r\n/).forEach(line => {
          if (/^\:$/.test(line)) resolve();
          if (/^\?$/.test(line)) reject(); // need to tell error code here
        })
      }
      this.on('data', listener).write(`${command}\r\n`);
    }).timeout(5000).finally(() => {
      this.removeListener('data', listener);
    });
  }
}