how you can implement OpenVPN in an Android app with Kotlin. To implement OpenVPN in your Android application, you'll typically use the OpenVPN for Android client app's API, or package the VPN functionality using the OpenVPN3 library. For this example, we will use OpenVPN for Android and demonstrate how to control the OpenVPN client from your app.
Step 1: Add Dependencies
First, you need to include the OpenVPN client library. To do this, add the dependency for OpenVPN in your build.gradle file:
dependencies {
implementation 'de.blinkt:openvpn:0.7.8'
}
If the library isn't available in Maven or the dependency fails to resolve, you can compile OpenVPN for Android from its source or use the OpenVPN Connect app, which provides intents to control it.
Step 2: Request Permissions
In your AndroidManifest.xml, add the following permissions:
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.BIND_VPN_SERVICE"/>
Step 3: Example OpenVPN Connection in Kotlin
This example shows how to start a VPN connection using the OpenVPN for Android client through an intent.
1. Create a simple VPN configuration using an .ovpn file. The .ovpn file should be in the assets folder or accessible via the file system.
2. Use an intent to launch the OpenVPN connection from your app.
import android.content.Intent
import android.net.Uri
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import java.io.InputStream
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val connectButton = findViewById<Button>(R.id.connect_vpn)
connectButton.setOnClickListener {
startOpenVPN()
}
}
private fun startOpenVPN() {
// Path to your VPN configuration file stored in assets or external storage
val inputStream: InputStream = assets.open("your_vpn_config.ovpn")
val ovpnConfig = inputStream.bufferedReader().use { it.readText() }
// Write the configuration to a temporary file
val configFile = File(cacheDir, "temp_config.ovpn")
configFile.writeText(ovpnConfig)
// Start OpenVPN for Android using intent
val intent = Intent("de.blinkt.openvpn.VPN_PROFILE")
intent.putExtra("de.blinkt.openvpn.VPN_PROFILE", Uri.parse(configFile.path).toString())
intent.setPackage("de.blinkt.openvpn")
try {
startActivityForResult(intent, 0)
} catch (e: Exception) {
e.printStackTrace()
}
}
}
Step 4: Setting up the VPN Configuration
Place your .ovpn configuration file in the assets folder of your project.
Ensure that the .ovpn configuration has the correct settings for your VPN server (e.g., the remote server address, credentials, and certificates).
Notes:
OpenVPN for Android app must be installed on the device for this approach to work, as this app handles the actual VPN connection.
The configuration file (your_vpn_config.ovpn) should include server details and authentication information.
Step 5: Handling the Result
You can handle the VPN connection's result (success or failure) in the onActivityResult method:
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (resultCode == RESULT_OK) {
// VPN successfully connected
} else {
// VPN connection failed
}
}
Summary:
This example demonstrates how to use an intent to launch the OpenVPN for Android client from your app to establish a VPN connection. This approach simplifies the process by offloading most of the connection logic to the OpenVPN client, while your app handles the configuration and starting of the VPN.
