## 3 Design and Implementation of the Solution
An important part is the correct setting of the conditions, which are the same on both the module and the application side. Communication between the mobile application and the NFC module works on the  
Figure 6: System architecture of the designed Android application and its basic functionalities. principle of active operating mode. The mobile communication device simulates a passive NFC tag. In this case, the numerical value of the APDU is simulated, which consists of the patient ID and the procedure for which the patient attended. The NFC reader initiates communication between devices. For proper communication between the NFC reader and the mobile application, the correct setting of the mobile device as a card emulator was necessary. Communication is initiated by the NFC reader, which sends specific protocols, in the case of the application, AID F0654F6E6B6F00 is entered. The mobile device verifies the defined AID according to the settings in the mobile application. The identifier in the mobile application is defined in the aid_list.xml file. A check to support the use of NFC HCE must be included in the mobile application. For communication, it is necessary to have the NFC function enabled on the mobile communication device. The availability of the HCE service is conditional on the minimum OS version Android 4.4. FIREBASE_HOST, FIREBASE_AUTH, and API_KEY must be defined in the ESP8266 to ensure a proper connection between the mobile communication device and the real-time database using the NFC module. Defined variables are used to set up a real-time database connection. If the communication runs smoothly and the data requested by us is sent from the mobile application, the NFC reader will receive the information, which will be sent to the ESP8266 via the I2C bus. The information is further processed into data sent by ESP. Processing takes place using ordering and filtering. These steps perform ID identification and action from the received APDU value. The identified data will then be sent via Wi-Fi to the database in real-time, where they will be displayed in the ambulance-patient record. Calendar: in addition to emulating the card, the mobile application also provides an environment that allows patients to record the side-effects they experience during treatment. During the treatment, the patient notes unwanted effects, which he evaluates according to the scale. The scale is represented by smileys and is based on the CTC-SWOG scale. The scale is adjusted based on the patients' experiences with the mobile application. Ratings range from 1 to 5, with each value corresponding to words such as terrible, okay, or great. The patient sorts the individual daily records into trends that can be viewed. Numerical interpretation of the recorded data is used to display the recorded data, using emoticon evaluation. This activity provides the patient with a quick and general overview of their health status during the recording and offers the ability to delete the records in  
Figure 7: Final Android application: initial screen, patient registering process, and ID card activity. the table through an active floating button. Recording results also brings efficiency to the surgery. Based on the side-effects, the doctor can identify problems caused by radiotherapy or chemotherapy and can subsequently reduce the prevailing side-effects when using other drugs.