MQTT with Android

Question

I'm trying to publish a message via MQTT. So I created a blank Android app and added the Paho MQTT library to it.

This is the line of code I execute first:

MqttClient client = new MqttClient("tcp://192.168.178.34", "Foo");

This throws an "MqttException" which contains no message, no error code, no nothing. So currently I have no idea what's going wrong.

I also added the following permissions to my app:

<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

Can anyone give me a hint what I could be doing wrong here?

Any reason you are using the raw client and not the Android Client? — hardillb, Jul 23 '17 at 15:51
Because its simpler and synchronous (which is what I need). I don't use TLS. Also the error occurs even before I call "connect". — Boris, Jul 23 '17 at 16:48
Add the exception stack trace to the question then we can see exactly where it's been thrown from — hardillb, Jul 24 '17 at 06:24

score 0 · Answer 1 · answered Aug 07 '17 at 08:00

In the code, The activated class is the TCPNetworkModule class which is using connect method of the socket class directly(see the start method of the class).

I think the exception might be the NetworkOnMainThreadException attempting to use blocking IO.

That's why we use MqttAndroidClient instead.

MQTT with Android

1 Answers1