# VPN Interface

The VPN Interface allows you to configure and control VPN sessions using the `UnifiedSDK` class. This document provides an overview of the available methods and classes for managing VPN sessions.

## SessionConfig

The `SessionConfig` class is used to configure VPN sessions. It provides the following `Builder` methods:

* `withTransport(transportName)` - Set the transport name to start the session with. Useful when multiple transports are available.
* `withPolicy(appPolicy)` - Define the app policy to use. Available options:
  * `AppPolicy.forAll()` - VPN will be available for all apps.
  * `AppPolicy.newBuilder().policy(AppPolicy.POLICY_FOR_LIST)` - Specify a list of apps allowed to use VPN.
  * `AppPolicy.newBuilder().policy(AppPolicy.POLICY_EXCEPT_LIST)` - Specify a list of apps not allowed to use VPN.
* `withReason(reason)` - Define the reason for starting the session using `unified.vpn.sdk.TrackingConstants.GprReasons`. Used for analytics.
* `withLocation(location)` - Define the virtual location for the session.
* `withCountry(country)` - Define the virtual country for the session.
* `withPrivateGroup(group)` - Define a private server for the session.
* `withVpnParams(params)` - Define VPN tunnel parameters, such as DNS servers and additional routes.
* `addDnsRule(rule)` - Add a DNS rule for the session. More on [Traffic rules](/paas/sdk/vpn-sdk-for-android/features/traffic-rules.md) page. *For Hydra transport only.*
* `addProxyRule(rule)` - Add a proxy rule for the session. More on [Traffic rules](/paas/sdk/vpn-sdk-for-android/features/traffic-rules.md) page. *For Hydra transport only.*
* `withFireshieldConfig(config)` - Define categorization service rules. *For Hydra transport only*
* `withTransportFallback(fallbackOrder)` - Define the order of transports to fallback when an error occurs.
* `keepVpnOnReconnect()` - Enable the kill switch to prevent traffic while the SDK is in the connection process or handling connection errors.

## Examples

### Start VPN with an optimal server

```java
final SessionConfig session = new SessionConfig.Builder()
                .withLocation(UnifiedSDK.COUNTRY_OPTIMAL)
                .withReason(TrackingConstants.GprReasons.M_UI)
                .build();
```

### Start VPN for chrome only

```java
final List<String> apps = new ArrayList<String();
apps.add("com.google.chrome");
final SessionConfig session = new SessionConfig.Builder()
                .withLocation(UnifiedSDK.COUNTRY_OPTIMAL)
                .withReason(TrackingConstants.GprReasons.M_UI)
                .appPolicy(AppPolicy.newBuilder().policy(AppPolicy.POLICY_FOR_LIST).appList(apps).build())
                .build();
```

### Analytics Reasons

The following constants are used to specify the reason for starting the VPN session:

* `M_UI` - Manually started from the user interface
* `M_SYSTEM` - Manually started from the system
* `M_OTHER` - Manually started from another place
* `A_APP_RUN` - Automatically started on app run
* `A_RECONNECT` - Automatically started on reconnect
* `A_ERROR` - Automatically started after an error
* `A_SLEEP` - Automatically started after sleep
* `A_NETWORK` - Automatically started on a network event
* `A_OTHER` - Automatically started for other reasons

These constants are defined in the `TrackingConstants.GprReasons` enum and can be used with the `withReason` method when building the `SessionConfig`.

## Starting a VPN session

To start a VPN session:

```java
final SessionConfig sessionConfig = new SessionConfig.Builder()
    .build()

sdk.getVpn().start(sessionConfig, new CompletableCallback() {
    @Override
    public void complete() {
        // Handle successful completion of VPN start
    }

    @Override
    public void error(@NonNull VpnException e) {
        // Handle error during VPN start
    }
});
```

1. Obtain an instance of the `UnifiedSdk` class by calling the `getInstance()` method.
2. Create a `SessionConfig` object using the `SessionConfig.Builder` class. You can customize the session configuration by [setting various options in the builder](/paas/sdk/vpn-sdk-for-android/usage/vpn-interface.md).
3. Start the VPN session by calling the `start()` method on the `getVpn()` instance of the `UnifiedSdk`.

* The `complete()` method will be called when the VPN session starts successfully. You can add your logic to handle the successful start of the VPN here.
* The `error()` method will be called if an error occurs during the VPN start process. You can handle the error case and take appropriate actions based on the `VpnException` received.

{% hint style="info" %}
Make sure you have the necessary permissions and configurations in your Android manifest file for the VPN functionality to work properly.
{% endhint %}

## Stopping a VPN Session

To stop a VPN session:

```java
sdk.getVpn().stop(TrackingConstants.GprReasons.M_UI, new CompletableCallback() {
    @Override
    public void complete() {
        // VPN session stopped successfully
    }

    @Override
    public void error(@NonNull VpnException e) {
        // Failed to stop VPN session
    }
});
```

## Restarting a VPN Session

To restart a VPN session with a new configuration without entering the IDLE state:

```java
final SessionConfig session = //create session config
sdk.getVpn().restart(session, new CompletableCallback() {
    @Override
    public void complete() {
        // VPN session restarted successfully
    }

    @Override
    public void error(@NonNull VpnException e) {
        // Failed to restart VPN session
    }
});
```

## Updating Session Configuration

You can update certain VPN session configurations without restarting the VPN session. Currently, the SDK supports updating the following for the Hydra transport:

* Fireshield rules
* DNS Rules
* Proxy Rules

Example:

```java
final SessionConfig session = //create session config
sdk.getVpn().updateConfig(session, new CompletableCallback() {
    @Override
    public void complete() {
        // Session configuration updated successfully
    }

    @Override
    public void error(@NonNull VpnException e) {
        // Failed to update session configuration
    }
});
```

## Listening for VPN Status and Traffic Updates

To listen for VPN status and traffic updates:

```java
UnifiedSDK.addVpnStateListener(new VpnStateListener() {
    @Override
    public void vpnStateChanged(@NonNull VpnState vpnState) {
        // Handle VPN state change
    }

    @Override
    public void vpnError(@NonNull VpnException e) {
        // Handle VPN error
    }
});

UnifiedSDK.addTrafficListener(new TrafficListener() {
    @Override
    public void onTrafficUpdate(long rx, long tx) {
        // Handle traffic update
    }
});

// To stop listening for updates
UnifiedSDK.removeTrafficListener(...);
UnifiedSDK.removeVpnStateListener(...);
```

## Getting Current VPN State

To get the current VPN state:

```java
UnifiedSDK.getVpnState(new Callback<VpnState>() {
    @Override
    public void success(@NonNull VpnState vpnState) {
        // Handle VPN state
    }

    @Override
    public void failure(@NonNull VpnException e) {
        // Handle failure to get VPN state
    }
});
```

## VPN States

* **IDLE** - No active VPN session.
* **CONNECTING\_PERMISSIONS** - Requesting system VPN permission.
* **CONNECTING\_CREDENTIALS** - Loading backend information to establish a connection.
* **CONNECTING\_VPN** - Transport connection in progress.
* **DISCONNECTING** - Disconnection started.
* **CONNECTED** - VPN session is active and connected.
* **PAUSED** - VPN session paused due to an error, network change, or waiting to restore the VPN session.
* **UNKNOWN** - Not used, reserved.
* **ERROR** - Not used, reserved.

## Checking VPN Permissions

To check if the app has system VPN permissions granted:

```java
final boolean granted = VpnPermissions.granted();
```

To request VPN permissions without connecting to the VPN:

```java
VpnPermissions.request(new CompletableCallback() {
    @Override
    public void complete() {
        // Permission granted
    }

    @Override
    public void error(@NonNull VpnException e) {
        // Failed to get permission
    }
});
```

## Getting Current VPN Session Information

To get the current VPN session information:

```java
UnifiedSdk.getStatus(new Callback<SessionInfo>() {
    @Override
    public void success(@NonNull SessionInfo sessionInfo) {
        // Handle session information (e.g., get sessionInfo.getConnectionStatus().getSuccessInfo())
    }

    @Override
    public void failure(@NonNull VpnException e) {
        // Handle failure to get session information
    }
});
```


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