# Use tokens (/en/realtime-media/voice/build/set-up-token-authentication/use-tokens/android)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

To protect your business, it is best practice to authenticate every client that joins a channel. This guide explains how to fetch an authentication token from your token server, use it to join a channel, and renew the token when it expires.

## Understand the tech [#understand-the-tech]

      
    When a user attempts to connect to an Agora channel, your app retrieves a token from the token server in your security infrastructure. Your app then sends this token to Agora SDRTN® for authentication. Agora SDRTN® reads the information stored in the token to validate the request.

    The following figure shows the call flow you implement to create step-up-authentication with Agora Voice Calling:

    **Token authentication flow**

    ![token authentication flow](https://assets-docs.agora.io/images/video-sdk/token-authentication.svg)

    ## Prerequisites [#prerequisites]

    Before starting, ensure that you have:

    * Implemented the [Quickstart](../index.mdx) in your project.

    * Deployed a token server using either of the following guides:

      * [Deploy a token server](deploy-token-server.mdx)
      * [Deploy a middleware server](middleware-token-server.md)

    ## Implement basic authentication [#implement-basic-authentication]

    This section shows you how to implement basic authentication by acquiring a token and using it to join a channel.

    ### Use a token to join a channel [#use-a-token-to-join-a-channel]

    The client requests a token from your authentication server corresponding to the user ID and the channel name. You use the received token to join a channel.

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      <CodeBlockTab value="java">
        ```java
        // Channel name
        String channelId = "xxx";
        // User ID
        int uid = 0;
        // Request a token from the server corresponding to channelId and uid
        String token = getToken(channelId, uid);
        // Set channel media options
        ChannelMediaOptions option = new ChannelMediaOptions();
        option.clientRoleType = Constants.CLIENT_ROLE_BROADCASTER;
        // Join a channel
        engine.joinChannel(token, channelId, 0, option);
        ```
      </CodeBlockTab>

      <CodeBlockTab value="kotlin">
        ```kotlin
        // Channel name
        val channelId = "xxx"
        // User ID
        val uid = 0
        // Request a token from the server corresponding to channelId and uid
        val token = getToken(channelId, uid)
        // Set channel media options
        val option = ChannelMediaOptions().apply {
          clientRoleType = Constants.CLIENT_ROLE_BROADCASTER
        }
        // Join a channel
        engine.joinChannel(token, channelId, 0, option)
        ```
      </CodeBlockTab>
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    ### Token expiration [#token-expiration]

    After you join a channel using a token, the SDK triggers an `onTokenPrivilegeWillExpire` callback, 30 seconds before the token is set to expire.

    When the token expires, the SDK triggers an `onRequestToken` callback. After receiving the callback, you regenerate a new token on the server side, and then update the token in one of the following ways:

    #### Single channel use-case [#single-channel-use-case]

    * Call `renewToken` to pass in the newly generated Token (Recommended).

    * Call `updateChannelMediaOptions` to update the token.

    * Call `leaveChannel` \[2/2] to leave the current channel, and then pass in a new token when calling `joinChannel` \[2/2] to rejoin the channel.

    #### Multi-channel use-case [#multi-channel-use-case]

    If you call `joinChannelEx` to join multiple channels, call the `updateChannelMediaOptionsEx` method to update the token.

    The following sample code demonstrates how to call `renewToken` to update the token upon receiving an `onTokenPrivilegeWillExpire` callback notification.

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        ```java
        class RtcEngineEventHandlerImpl extends IRtcEngineEventHandler {
          // Callback is triggered when the token is about to expire
          @Override
          public void onTokenPrivilegeWillExpire(String token) {
            super.onTokenPrivilegeWillExpire(token);

            // Request to generate a fresh token
            String token = getToken();
            // Update token
            engine.renewToken(token);
          }
        }
        ```
      </CodeBlockTab>

      <CodeBlockTab value="kotlin">
        ```kotlin
        class RtcEngineEventHandlerImpl : IRtcEngineEventHandler() {
          // Callback triggered when the token is about to expire
          override fun onTokenPrivilegeWillExpire(token: String) {
            super.onTokenPrivilegeWillExpire(token)

            // Request to generate a fresh token
            val newToken = getToken()
            // Update the token
            engine.renewToken(newToken)
          }
        }
        ```
      </CodeBlockTab>
    </CodeBlockTabs>

    ### Complete sample code [#complete-sample-code]

    This section presents sample code to implement token authentication in your client.

    1. In `/Gradle Scripts/build.gradle(Module: <projectname>.app)`, add the following dependencies for making HTTP requests to the token server:

       ```yaml
       dependencies {
        implementation 'com.squareup.okhttp3:okhttp:3.10.0'
        implementation 'com.google.code.gson:gson:2.8.4'
       }
       ```

    2. In `MainActivity`, replace the content with the following code:

       **Complete sample code for token authentication**

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        ```java
        package com.example.rtcquickstart;
          import androidx.appcompat.app.AppCompatActivity;
          import android.os.Bundle;
          import androidx.core.app.ActivityCompat;
          import androidx.core.content.ContextCompat;

          import android.Manifest;
          import android.content.pm.PackageManager;
          import android.view.SurfaceView;
          import android.widget.FrameLayout;
          import android.widget.Toast;
          import io.agora.rtc2.Constants;
          import io.agora.rtc2.IRtcEngineEventHandler;
          import io.agora.rtc2.RtcEngine;
          import io.agora.rtc2.video.VideoCanvas;
          import io.agora.rtc2.ChannelMediaOptions;

          import okhttp3.MediaType;
          import okhttp3.OkHttpClient;
          import okhttp3.Request;
          import okhttp3.RequestBody;
          import okhttp3.Response;
          import okhttp3.Call;
          import okhttp3.Callback;

          import com.google.gson.Gson;
          import java.util.Map;
          import org.json.JSONException;
          import org.json.JSONObject;
          import java.io.IOException;

          public class MainActivity extends AppCompatActivity {

           // Fill in the App ID from Agora console
           private String appId = "Your App ID";
           // Fill in the channel name
           private String channelName = "demo";
           private String token = "";
           private RtcEngine mRtcEngine;
           private int joined = 1;

           private final IRtcEngineEventHandler mRtcEventHandler = new IRtcEngineEventHandler() {
             @Override
             public void onUserJoined(int uid, int elapsed) {
                runOnUiThread(() -> setupRemoteVideo(uid));
             }

             @Override
             public void onTokenPrivilegeWillExpire(String token) {
                fetchToken(1234, channelName, 1);
                runOnUiThread(() -> {
                 Toast toast = Toast.makeText(MainActivity.this, "Token renewed", Toast.LENGTH_SHORT);
                 toast.show();
                });
                super.onTokenPrivilegeWillExpire(token);
             }

             @Override
             public void onRequestToken() {
                joined = 1;
                fetchToken(1234, channelName, 1);
                super.onRequestToken();
             }
           };

           private static final int PERMISSION_REQ_ID = 22;

           private static final String[] REQUESTED_PERMISSIONS = {
                Manifest.permission.RECORD_AUDIO,
                Manifest.permission.CAMERA
           };

           private boolean checkSelfPermission(String permission, int requestCode) {
             if (ContextCompat.checkSelfPermission(this, permission) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, REQUESTED_PERMISSIONS, requestCode);
                return false;
             }
             return true;
           }

           // Get RTC Token
           private void fetchToken(int uid, String channelName, int tokenRole) {
             OkHttpClient client = new OkHttpClient();
             MediaType JSON = MediaType.parse("application/json; charset=utf-8");
             JSONObject json = new JSONObject();
             try {
                json.put("uid", uid);
                json.put("ChannelName", channelName);
                json.put("role", tokenRole);
             } catch (JSONException e) {
                e.printStackTrace();
             }

             RequestBody requestBody = RequestBody.create(JSON, String.valueOf(json));
             Request request = new Request.Builder()
                 .url("http://<Your Host URL and port>/fetch_rtc_token")
                 .header("Content-Type", "application/json; charset=UTF-8")
                 .post(requestBody)
                 .build();
             Call call = client.newCall(request);
             call.enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                 if (response.isSuccessful()) {
                   Gson gson = new Gson();
                   String result = response.body().string();
                   Map map = gson.fromJson(result, Map.class);
                   new Thread(() -> {
                      token = map.get("token").toString();
                      ChannelMediaOptions options = new ChannelMediaOptions();
                      if (joined != 0) {
                       joined = mRtcEngine.joinChannel(token, channelName, 1234, options);
                      } else {
                       mRtcEngine.renewToken(token);
                      }
                   }).start();
                 }
                }
             });
           }

           @Override
           protected void onCreate(Bundle savedInstanceState) {
             super.onCreate(savedInstanceState);
             setContentView(R.layout.activity_main);

             if (checkSelfPermission(REQUESTED_PERMISSIONS[0], PERMISSION_REQ_ID) &&
                 checkSelfPermission(REQUESTED_PERMISSIONS[1], PERMISSION_REQ_ID)) {
                initializeAndJoinChannel();
             }
           }

           @Override
           protected void onDestroy() {
             super.onDestroy();
             mRtcEngine.leaveChannel();
             mRtcEngine.destroy();
           }

           private void initializeAndJoinChannel() {
             try {
                mRtcEngine = RtcEngine.create(getBaseContext(), appId, mRtcEventHandler);
             } catch (Exception e) {
                throw new RuntimeException("Check the error.");
             }

             mRtcEngine.setChannelProfile(Constants.CHANNEL_PROFILE_LIVE_BROADCASTING);
             mRtcEngine.setClientRole(Constants.CLIENT_ROLE_BROADCASTER);
             mRtcEngine.enableVideo();

             FrameLayout container = findViewById(R.id.local_video_view_container);
             SurfaceView surfaceView = new SurfaceView(getBaseContext());
             container.addView(surfaceView);
             mRtcEngine.setupLocalVideo(new VideoCanvas(surfaceView, VideoCanvas.RENDER_MODE_FIT, 0));
             mRtcEngine.startPreview();
             fetchToken(1234, channelName, 1);
           }

           private void setupRemoteVideo(int uid) {
             FrameLayout container = findViewById(R.id.remote_video_view_container);
             SurfaceView surfaceView = new SurfaceView(getBaseContext());
             surfaceView.setZOrderMediaOverlay(true);
             container.addView(surfaceView);
             mRtcEngine.setupRemoteVideo(new VideoCanvas(surfaceView, VideoCanvas.RENDER_MODE_FIT, uid));
           }
          }
        ```
      </CodeBlockTab>

      <CodeBlockTab value="kotlin">
        ```kotlin
        package com.example.rtcquickstart

          import android.Manifest;
          import android.content.pm.PackageManager;
          import android.os.Bundle;
          import android.view.SurfaceView;
          import android.widget.FrameLayout;
          import android.widget.Toast;

          import androidx.appcompat.app.AppCompatActivity;
          import androidx.core.app.ActivityCompat;
          import androidx.core.content.ContextCompat;

          import io.agora.rtc2.*;
          import io.agora.rtc2.video.VideoCanvas;

          import com.google.gson.Gson;
          import okhttp3.*;
          import org.json.JSONException;
          import org.json.JSONObject;
          import java.io.IOException;
          import java.util.*;

          class MainActivity : AppCompatActivity() {

           // Fill in the App ID from Agora console
           private val appId = "Your App ID"
           // Fill in the channel name
           private val channelName = "demo"
           private var token = ""
           private var mRtcEngine: RtcEngine? = null
           private var joined = 1

           private val mRtcEventHandler = object : IRtcEngineEventHandler() {
             override fun onUserJoined(uid: Int, elapsed: Int) {
                runOnUiThread {
                 // After obtaining the user ID in the onUserJoined callback, call setupRemoteVideo to set the remote user view
                 setupRemoteVideo(uid)
                }
             }

             override fun onTokenPrivilegeWillExpire(token: String) {
                fetchToken(1234, channelName, 1)
                runOnUiThread {
                 val toast = Toast.makeText(this@MainActivity, "Token renewed", Toast.LENGTH_SHORT)
                 toast.show()
                }
                super.onTokenPrivilegeWillExpire(token)
             }

             override fun onRequestToken() {
                joined = 1
                fetchToken(1234, channelName, 1)
                super.onRequestToken()
             }
           }

           companion object {
             private const val PERMISSION_REQ_ID = 22
             private val REQUESTED_PERMISSIONS = arrayOf(
                Manifest.permission.RECORD_AUDIO,
                Manifest.permission.CAMERA
             )
           }

           private fun checkSelfPermission(permission: String, requestCode: Int): Boolean {
             return if (ContextCompat.checkSelfPermission(this, permission) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, REQUESTED_PERMISSIONS, requestCode)
                false
             } else {
                true
             }
           }

           // Get RTC Token
           private fun fetchToken(uid: Int, channelName: String, tokenRole: Int) {
             val client = OkHttpClient()
             val JSON = MediaType.parse("application/json; charset=utf-8")
             val json = JSONObject()
             try {
                json.put("uid", uid)
                json.put("ChannelName", channelName)
                json.put("role", tokenRole)
             } catch (e: JSONException) {
                e.printStackTrace()
             }

             val requestBody = RequestBody.create(JSON, json.toString())
             val request = Request.Builder()
                .url("http://<Your Host URL and port>/fetch_rtc_token")
                .header("Content-Type", "application/json; charset=UTF-8")
                .post(requestBody)
                .build()

             client.newCall(request).enqueue(object : Callback {
                override fun onFailure(call: Call, e: IOException) {
                 // Handle failure
                }

                override fun onResponse(call: Call, response: Response) {
                 if (response.isSuccessful) {
                   val gson = Gson()
                   val result = response.body?.string()
                   val map: Map<String, Any> = gson.fromJson(result, Map::class.java)
                   Thread {
                      token = map["token"].toString()
                      // If the user has not joined the channel, use token to join the channel
                      val options = ChannelMediaOptions()
                      if (joined != 0) {
                       joined = mRtcEngine?.joinChannel(token, channelName, 1234, options) ?: -1
                      } else {
                       mRtcEngine?.renewToken(token)
                      }
                   }.start()
                 }
                }
             })
           }

           override fun onCreate(savedInstanceState: Bundle?) {
             super.onCreate(savedInstanceState)
             setContentView(R.layout.activity_main)

             // If all permissions are granted, initialize the RtcEngine object and join the channel
             if (checkSelfPermission(REQUESTED_PERMISSIONS[0], PERMISSION_REQ_ID) &&
                checkSelfPermission(REQUESTED_PERMISSIONS[1], PERMISSION_REQ_ID)) {
                initializeAndJoinChannel()
             }
           }

           override fun onDestroy() {
             super.onDestroy()
             mRtcEngine?.leaveChannel()
             mRtcEngine?.destroy()
           }

           private fun initializeAndJoinChannel() {
             try {
                mRtcEngine = RtcEngine.create(baseContext, appId, mRtcEventHandler)
             } catch (e: Exception) {
                throw RuntimeException("Check the error.")
             }

             // In interactive live broadcast, set the channel scene to BROADCASTING
             mRtcEngine?.setChannelProfile(Constants.CHANNEL_PROFILE_LIVE_BROADCASTING)
             // Depending on the actual situation, set the user role to BROADCASTER or AUDIENCE
             mRtcEngine?.setClientRole(Constants.CLIENT_ROLE_BROADCASTER)

             // SDK turns off video by default. Call enableVideo to enable video
             mRtcEngine?.enableVideo()

             val container: FrameLayout = findViewById(R.id.local_video_view_container)
             // Call CreateRendererView to create a SurfaceView object and add it as a child to the FrameLayout
             val surfaceView = SurfaceView(baseContext)
             container.addView(surfaceView)
             // Pass the SurfaceView object to Agora to render local video
             mRtcEngine?.setupLocalVideo(VideoCanvas(surfaceView, VideoCanvas.RENDER_MODE_FIT, 0))
             // Start local video preview
             mRtcEngine?.startPreview()
             // Get a token from the token server
             fetchToken(1234, channelName, 1)
           }

           private fun setupRemoteVideo(uid: Int) {
             val container: FrameLayout = findViewById(R.id.remote_video_view_container)
             val surfaceView = SurfaceView(baseContext)
             surfaceView.setZOrderMediaOverlay(true)
             container.addView(surfaceView)
             mRtcEngine?.setupRemoteVideo(VideoCanvas(surfaceView, VideoCanvas.RENDER_MODE_FIT, uid))
           }
          }
        ```
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    <CalloutContainer type="info">
      <CalloutDescription>
        The user ID and channel name used to join a channel must be consistent with the values used to generate the token.
      </CalloutDescription>
    </CalloutContainer>

    ## Reference [#reference]

    This section contains content that completes the information on this page, or points you to documentation that explains other aspects to this product.

    ### API reference [#api-reference]

    * [`joinChannel` \[2/2\]](https://api-ref.agora.io/en/video-sdk/android/4.x/API/class_irtcengine.html#api_irtcengine_joinchannel2)

    * [`renewToken`](https://api-ref.agora.io/en/video-sdk/android/4.x/API/class_irtcengine.html#api_irtcengine_renewtoken)

    * [`onTokenPrivilegeWillExpire`](https://api-ref.agora.io/en/video-sdk/android/4.x/API/class_irtcengineeventhandler.html#callback_irtcengineeventhandler_ontokenprivilegewillexpire)