How to defend the rights of a hotel waiter who opens the door by mistake and is sued by a guest?

Collect evidence and actively respond to the defense.

People's Republic of China (PRC) Civil Procedure Law

Article 125 The people's court shall send a copy of the indictment to the defendant within five days from the date of filing the case, and the defendant shall submit a reply within fifteen days from the date of receiving the indictment. The defense shall specify the defendant's name, gender, age, nationality, occupation, work unit, residence and contact information; The name and domicile of the legal person or other organization and the name, position and contact information of the legal representative or principal responsible person. The people's court shall send a copy of the defense to the plaintiff within five days from the date of receiving the defense.

If the defendant fails to submit the defense, it will not affect the trial of the people's court.