The last day I explain how to upload a simple CSV file using node . And now I teach how to upload from android device. Get source code here: GitHub This article is write in java... later I'll add the method for kotlin. The logic is not changed, only the format code. 1) Is necessary add the dependencies in gradle: module implementation 'com.google.code.gson:gson:2.8.6' // RETROFIT // implementation 'com.squareup.retrofit2:retrofit:2.6.2' implementation 'com.squareup.retrofit2:converter-gson:2.6.2' implementation 'com.squareup.retrofit2:converter-scalars:2.5.0' 2) Add permissions in AndroidManifest.xml and modified the application for work with network security policy <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> in applitacion add ...