App Engine with Google Cloud Messaging

Question

I implemented the app engine module with Google Cloud Messaging, the devices are registrated succesfully and I deployed it live already. My question is, by doing a RESTful API with this integration, do I need to make a server side code, for sending push notifications, or can I send them through the client-side part?

Here´s my Android Manifest code:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="myPackage">
    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.Camera2"
        android:required="true" />
    <!-- This filters devices that don't support sip -->
    <uses-feature
        android:name="android.hardware.sip.voip"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.wifi"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.microphone"
        android:required="true" />
    <receiver
        android:name=".IncomingCallReceiver"
        android:label="Call Receiver" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.USE_CREDENTIALS" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <!-- [START gcm_permission] -->
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" >
    <!-- [END gcm_permission] -->
    <permission
        android:name="myPackage.permission.C2D_MESSAGE"
        android:protectionLevel="signature" />
    <uses-permission android:name="myPackage.permission.C2D_MESSAGE" />
    <application
        android:name=".MyApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name="com.facebook.FacebookActivity"
            android:configChanges="keyboard|keyboardHidden|screenLayout|screenSize|orientation"
            android:label="@string/app_name"
            android:theme="@android:style/Theme.Translucent.NoTitleBar" />
        <activity android:name=".LogInActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_app_id" />
        <meta-data
            android:name="com.facebook.sdk.ApplicationId"
            android:value="@string/facebook_app_id" />

        <activity android:name=".MainActivity" />
        <activity
            android:name=".Messaging.Activities.FriendsRequestsActivity"
            android:parentActivityName=".MainActivity">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>
        <activity
            android:name=".Messaging.Activities.ChatActivity"
            android:launchMode="singleTop"
            android:parentActivityName=".MainActivity"
            android:screenOrientation="portrait"
            android:theme="@style/ChatTheme"
            android:windowSoftInputMode="adjustResize|stateHidden">
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value=".MainActivity" />
        </activity>

        <receiver
            android:name="com.google.android.gms.gcm.GcmReceiver"
            android:exported="true"
            android:permission="com.google.android.c2dm.permission.SEND">
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                <category android:name="myPackage" />
            </intent-filter>
        </receiver>

        <service
            android:name=".Utils.InstanceIDListener"
            android:exported="false">
            <intent-filter>
                <action android:name="com.google.android.gms.iid.InstanceID" />
            </intent-filter>
        </service>

        <service
            android:name="myPackage.Utils.RegistrationIntent"
            android:exported="false"></service>

        <service
            android:name="myPackage.Utils.GcmListener"
            android:exported="false">
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
            </intent-filter>
        </service>
    </application>

</manifest>`

This is my GcmListener that receives that is supposed to be receiving the message:

public class GcmListener extends GcmListenerService {

    private static final String TAG = "Push";

    /**
     * Called when message is received.
     *
     * @param from SenderID of the sender.
     * @param data Data bundle containing message data as key/value pairs.
     *             For Set of keys use data.keySet().
     */
    // [START receive_message]
    @Override
    public void onMessageReceived(String from, Bundle data) {
        JSONObject jsonObject = new JSONObject();
        Log.d(TAG, "Push received");
        Set<String> keys = data.keySet();
        for (String key : keys) {
            try {
                jsonObject.put(key, data.get(key));
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        try {
            sendNotification("Received: " + jsonObject.toString(5));//TODO Forward to be written
        } catch (JSONException e) {
            e.printStackTrace();
        }

        if (from.startsWith("/topics/")) {
            // message received from some topic.
        } else {
            // normal downstream message.
        }

        // [START_EXCLUDE]
        /**
         * Production applications would usually process the message here.
         * Eg: - Syncing with server.
         *     - Store message in local database.
         *     - Update UI.
         */

        /**
         * In some cases it may be useful to show a notification indicating to the user
         * that a message was received.
         */
        //sendNotification(message); TODO create the correct notification to be showed to the user
        // [END_EXCLUDE]
    }
}

The sendNotification method is not written yet, but I put a log to check if the message was received, and I get nothing,I honestly think I used the wrong API_KEY from the Google Developers Console, I am using the: Server key (auto created by Google Service), or maybe the order of the declarations of the services in the manifest. Those are the only things that I can think of that could be causing the app not to get the push message

Answer 1

No need to build your own server if you just want to send message between two client device. Just send send your message with opponent's registration id and they will receive it. Anyway, if you want to store that message, you should build one.

You can create an object like this, put registration_ids and data you want to send in it

public class MessageSenderContent implements Serializable {
    private List<String> registration_ids;
    private Map<String, String> data;

    public void addRegId(String regId){
        if (registration_ids==null){
            registration_ids = new LinkedList<String>();
            registration_ids.add(regId);
        }
    }

    public void createData(String title,String message) {
        if (data == null)
            data = new HashMap<String, String>();

        data.put("title", title);
        data.put("message", message);
    }

    public Map<String, String> getData() {
        return data;
    }

    public void setData(Map<String, String> data) {
        this.data = data;
    }

    public List<String> getRegIds() {
        return registration_ids;
    }

    public void setRegIds(List<String> regIds) {
        this.registration_ids = regIds;
    }

    @Override
    public String toString() {
        return "MessageSenderContent{" +
                "registration_ids=" + registration_ids +
                ", data=" + data +
                '}';
    }

}

UPDATE 1 You need to put data to that object like this and make a http request to the server:

 private static MessageSenderContent createMegContent(String regId, String title) {
        String message = txt_chat.getText().toString();
        MessageSenderContent mgsContent = new MessageSenderContent();
        mgsContent.addRegId(regId);// add registration_id of the device you want to send
        mgsContent.createData(title, message);
        return mgsContent;
    }

UPDATE 2

This is my class that will send http request to the server:

public class MessageSender {

    private int responseCode;

    public boolean sendPost(MessageSenderContent content) {

        HttpURLConnection connection;
        try {
            URL gcmAPI = new URL("https://android.googleapis.com/gcm/send");
            connection = (HttpURLConnection) gcmAPI.openConnection();

            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type","application/json");
            connection.setRequestProperty("Authorization", "key=" + AppConfig.API_KEY); //api_key is what generate when you register a project  in google console
            connection.setDoOutput(true);
            ObjectMapper mapper = new ObjectMapper();         mapper.setVisibility(PropertyAccessor.FIELD,JsonAutoDetect.Visibility.ANY);
            DataOutputStream dataOutputStream = new DataOutputStream(connection.getOutputStream());

            mapper.writeValue(dataOutputStream, content);

            dataOutputStream.flush();
            dataOutputStream.close();

            responseCode = connection.getResponseCode();
        } catch (IOException e) {
            e.printStackTrace();
        }
        if (responseCode == 200) {
            Log.i("Request Status", "This is success response status from server: " + responseCode);
            return true;
        } else {
            Log.i("Request Status", "This is failure response status from server: " + responseCode);
            return false;
        }
    }
}

In my activity I will create an instance of it and use it to send MessageSenderContent to GCM server like this:

                    MessageSender mgsSender = new MessageSender();
                    new AsyncTask<Void, Void, Void>() {
                        @Override
                        protected Void doInBackground(Void... params) {
                            MessageSenderContent mgsContent = createMegContent(registration_Id, your_title);

                            mgsSender.sendPost(mgsContent)
                            return null;
                        }
                    }.execute();

Service manifest code:

        <service
            android:name="training.com.services.MessageListenerService"
            android:exported="false" >
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                <action android:name="android.intent.action.PHONE_STATE" />
            </intent-filter>
        </service>