func send(candidate rtcIceCandidate: RTCIceCandidate, to person: String) {
    do {
      let dataMessage = try self.encoder.encode(IceCandidate(from: rtcIceCandidate))
      let dict = try JSONSerialization.jsonObject(with: dataMessage, options: .allowFragments) as! [String: Any]
      Firestore.firestore()
        .collection(person)
        .document("candidate")
        .collection("candidates")
        .addDocument(data: dict) { (err) in
          if let err = err {
            print("Error send candidate: \(err)")
          } else {
            print("Candidate sent!")
          }
      }
    }
    catch {
      debugPrint("Warning: Could not encode candidate: \(error)")
    }
  }