Tag: mqtt

Mosquitto 1.6.8 With Websockets Becomes Unresponsive

When I installed software on our new server, I got the “latest and greatest”. And have found that my mosquitto server hangs after about 20 minutes. No errors. Even strace doesn’t show anything beyond it not doing anything. I am able to use the command line utilities to confirm that the service isn’t there even though it looks like it is working.

Subscribe to the subtree of a topic:

mosquitto_sub -h mqtt.example.com -t testtopic/#

Publish a message to a topic:

mosquitto_pub -h mqtt.example.com -t testtopic/data/lisa -m "Test4"

To test WebSockets, I’ve put together a Python script that subscribes to a topic. Changing the commented lines switches between the WebSocket reverse proxy, the old and new MQTT servers via WebSockets, and the old and new MQTT servers directly in an attempt to isolate what is wrong.

import sys
import paho.mqtt.client as mqtt

def on_connect(mqttc, obj, flags, rc):
    print(f"rc: {str(rc)}")

def on_message(mqttc, obj, msg):
    print(f"{datetime.datetime.now()}: {msg.topic} {str(msg.qos)} {str(msg.payload)}")

def on_publish(mqttc, obj, mid):
    print(f"mid: {str(mid)}")

def on_subscribe(mqttc, obj, mid, granted_qos):
    print(f"Subscribed at {datetime.datetime.now()}: {str(mid)} {str(granted_qos)}")
def on_log(mqttc, obj, level, string):
    print(string)
# Client uses websockets
mqttc = mqtt.Client(transport='websockets', client_id="ljrTestingPythonScript", clean_session=False)
# Client uses MQTT directly
#mqttc = mqtt.Client(client_id="ljrTestingPythonScript", clean_session=False)

mqttc.username_pw_set("whateveruser", "wh@t3v3rP@s5w0rd")
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_publish = on_publish
mqttc.on_subscribe = on_subscribe

#mqttc.connect("oldmosquitto.example.com", 80, 60)
mqttc.connect("newmosquitto.example.com", 80, 60)
#mqttc.connect("newmqtt.example.com", 1883, 60)
#mqttc.connect("newmqtt.example.com", 9001, 60)
#mqttc.connect("oldmqtt.example.com", 1883, 60)
#mqttc.connect("oldmqtt.example.com", 9001, 60)

mqttc.subscribe("owntracks/#", 0)

mqttc.loop_forever()

None of this helped, unfortunately. The reverse proxy couldn’t communicate with the MQTT server because it was unresponsive. Attempting to communicate with the server directly fails too.

I see a few issues in the Mosquitto repository that are similar — and the current discussion indicates that libwebsockets 3.2.0 introduced some incompatibility that they’ve addressed in Mosquitto 1.6.7 … since my problem relates to WebSockets, I wanted to try running the iteration before whatever changed.

git clone --branch v3.1.0 https://libwebsockets.org/repo/libwebsockets
cd libwebsockets
mkdir build
cd build
cmake ..
make
make install

git clone --branch v1.6.2 https://github.com/eclipse/mosquitto.git
cd mosquitto
vi config.mk # Change WITH_WEBSOCKETS:=no to :=yes
make
make install

ln -s /usr/local/lib/libwebsockets.so.14 /lib64/
ln -s /usr/local/lib/libmosquitto.so.1 /usr/lib64/libmosquitto.so.1

/usr/local/sbin/mosquitto -v -c /etc/mosquitto/mosquitto.conf

We’ll see if this is more reliable. It’s been up for 30 minutes … which is longer than the 1.6.8 iteration managed to run.

Owntracks Stuck In “Connecting” To MQTT When Using WebSockets

Our home automation presence is maintained through an Android app, OwnTracks, which updates a Mosquitto server via a WebSockets reverse proxy. Mosquitto runs on a Fedora 25 server and was installed from the default RPM repository.

Recently, we stopped receiving location updates – both of our Android clients were stuck “Connecting” to the MQTT server. Nothing appeared in the Apache access or error logs, and capturing network traffic only got a small number of packets (TCP session overhead ‘stuff’). Even bypassing the reverse proxy and using the internal network to communicate directly to the Mosquitto server only created a couple of packets. Using a test client (http://www.hivemq.com/demos/websocket-client/), I saw strange connection failures — so I knew the problem was not specific to the OwnTracks client.

It seems there was a bug in libwebsockets v2.1.1 (and possibly others) — when we updated our Fedora installation, the new libwebsockets broke our MQTT over WebSockets. Currently, the Fedora repository still contains an impacted version of libwebsockets. To resolve the issue, I built the latest stable libwebsockets and built mosquitto against this updated library.

Process: The first step is to remove the dnf managed packages (rpm -e libwebsockets libwebsockets-devel mosquitto). Then build libwebsockets and mosquitto.

To Build LibWebSockets:

wget https://github.com/warmcat/libwebsockets/archive/master.zip
unzip master.zip
cd libwebsockets-master/
mkdir build
cd build
cmake ..
make
make install
cp libwebsockets.pc /usr/lib/
cp lws_config.h /usr/include/
cp ../lib/libwebsockets.h /usr/include/
cp ./lib/libwebsockets.so /usr/lib/

To Build Mosquitto:

wget https://github.com/eclipse/mosquitto/archive/master.zip
unzip master.zip
cd mosquitto-1.4.11
vi config.mk # Line 68, change to “WITH_WEBSOCKETS:=yes”
make
make install

Start the Mosquitto server and try again. Voila, presence works again!