# Secure authentication with tokens (/en/realtime-media/iot/build/set-up-authentication-and-security/authentication-workflow)

> 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 IoT SDK:

**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.md) in your project.

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

  * [Deploy a token server](/en/realtime-media/video/build/authenticate-users/deploy-token-server)
  * [Deploy a middleware server](/en/realtime-media/video/build/authenticate-users/middleware-token-server)

## 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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    ```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)
    ```
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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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     <CodeBlockTab value="java">
       ```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));
             }
          }
       ```
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     <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="warning">
  <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]

* [AgoraRtcService](https://api-ref.agora.io/en/iot-sdk/android/1.x/classio_1_1agora_1_1rtc_1_1_agora_rtc_service.html)

* [AgoraRtcEvents](https://api-ref.agora.io/en/iot-sdk/android/1.x/interfaceio_1_1agora_1_1rtc_1_1_agora_rtc_events.html)