使用Android在AWS IoT服务上发布MQTT消息

Question

I am trying to publish a mqtt message using AWSIotMqttManager with amazon web services IoT on an android app, i have follow used this example as a base to my code. The app says it can successfully connect to the device but fails to actually publish a message, what is wrong here?

// Initialize the AWS Cognito credentials provider
        credentialsProvider = new CognitoCachingCredentialsProvider(
                getApplicationContext(), // context
                COGNITO_POOL_ID, // Identity Pool ID
                MY_REGION // Region
        );
        Region region = Region.getRegion(MY_REGION);

        //intialize unnqique clientid as client to iot aws
        Long tsLong = System.currentTimeMillis()/1000;
        clientId = tsLong.toString();
// MQTT Client
        mqttManager = new AWSIotMqttManager(clientId, CUSTOMER_SPECIFIC_ENDPOINT);
// The following block uses a Cognito credentials provider for authentication with AWS IoT.
        new Thread(new Runnable() {
            @Override
            public void run() {
                awsCredentials = credentialsProvider.getCredentials();

                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        bttnConnect.setEnabled(true);
                        Toast.makeText(WelcomePageActivity.this, "credentials ok?", Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }).start();
//connection button onclick lisetner will connect to the mqtt protocol
        bttnConnect.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.d("LOG_TAG", "clientId = " + clientId);
                try {
                    mqttManager.connect(credentialsProvider, new AWSIotMqttClientStatusCallback() {
                        @Override
                        public void onStatusChanged(final AWSIotMqttClientStatus status,
                                                    final Throwable throwable) {
                            Log.d("LOG_TAG", "Status = " + String.valueOf(status));

                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    if (status == AWSIotMqttClientStatus.Connecting) {
                                        tvStatus.setText("Connecting...");

                                    } else if (status == AWSIotMqttClientStatus.Connected) {
                                        tvStatus.setText("Connected");

                                    } else if (status == AWSIotMqttClientStatus.Reconnecting) {
                                        if (throwable != null) {
                                            Log.e("LOG_TAG", "Connection error.", throwable);
                                        }
                                         tvStatus.setText("Reconnecting");
                                    } else if (status == AWSIotMqttClientStatus.ConnectionLost) {
                                        if (throwable != null) {
                                            Log.e("LOG_TAG", "Connection error.", throwable);
                                            throwable.printStackTrace();
                                        }
                                        tvStatus.setText("Disconnected");
                                    } else {
                                        tvStatus.setText("Disconnected");

                                    }
                                }
                            });
                        }
                    });

                } catch (final Exception e) {
                    Log.e("LOG_TAG", "Connection error.", e);
                    tvStatus.setText("Error! " + e.getMessage());
                }
            }
        });
       //publisj button
        ledbutton.setOnClickListener(new View.OnClickListener() {
            final String topic = "$aws/things/industech/shadow/update";
            final String msg = "{\"state\": {\"desired\": {\"ledBarStatus\": 1},\"reported\": {\"temperature\": 25,\"ledBarStatus\":1}}}";

            @Override
            public void onClick(View v) {
                try {
                   mqttManager.publishString(msg, topic, AWSIotMqttQos.QOS1);
                } catch (Exception e) {
                    Log.e("LOG_TAG", "Publish error.", e);
                }
            }
        });

The Log:

/CognitoCachingCredentialsProvider: Loading credentials from SharedPreferences

D/CognitoCachingCredentialsProvider: Saving credentials to SharedPreferences

D/LOG_TAG: clientId = 1489081527

D/LOG_TAG: Status = Connecting

D/LOG_TAG: Status = Connected

D/LOG_TAG: Status = Reconnecting

D/LOG_TAG: Status = Connected

Answer 1

Thanks for using AWS IoT Device SDK. Are you able to use your credentials to run the AndroidPubSubSample program and are you able to successfully subscribe and publish messages? This is to make sure you have the right credentials setup eg correct Policies and permissions attached.

In addition, you can subscribe to life cycle events "$aws/events/#" to see the log of your subscription and publish. I could successfully publish your JSON data to $aws/things/../update topics and got accepted on $aws.things/.../update/accepted by hardcoding topic and message.

If you have more questions and issues about using AWS IoT Device SDK, feel free to open an issue on the github repo. For Android SDK specifically, you can go to https://github.com/aws/aws-sdk-android

Answer 2

I believe the error is because you couldn't subscribe to a topic. Subscribe uses "topicfilter" in the IAM Policy statement whereas Publish and Receive uses "topic". The policy in the example is incorrect. The working IAM Policy is as follows:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "iot:Connect"
            ],
            "Resource": [
                "*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "iot:Publish",
                "iot:Receive"
            ],
            "Resource": [
                "arn:aws:iot:<your region>:<youracc>:topic/whatevertopic/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "iot:Subscribe"
            ],
            "Resource": [
                "arn:aws:iot:<your region>:<youracc>:topicfilter/whatevertopic/*"
            ]
        }
    ]
}