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Troubleshooting MQTT clients

Look for a troubleshooting task to help you solve a problem with running MQTT clients.

Location of telemetry logs, error logs, and configuration files
Find the logs, error logs, and configuration files used by IBM® WebSphere® MQ Telemetry.
MQTT v3 Java client reason codes
Look up the causes of reason codes in an MQTT v3 Java client exception or throwable.
Tracing the telemetry (MQXR) service
Follow these instructions to start a trace of the telemetry service, set the parameters that control the trace, and find the trace output.
Tracing the MQTT v3 Java client
Follow these instructions to create an MQTT Java client trace and control its output.
Tracing the MQTT client for C
Set the environment variable MQTT_C_CLIENT_TRACE to trace an MQTT client C app
Tracing and debugging the MQTT (Paho) Java client
The default logger uses the standard Java logging facility which is known as java.util.logging (JSR47). You can configure it either by the use of a configuration file or programmatically.
Tracing the MQTT JavaScript client
You can use the JavaScript client to collect trace by altering the client web application to call methods on the connected client object.
System requirements for using SHA-2 cipher suites with MQTT clients
For Java 6 from IBM, SR13 onwards, you can use SHA-2 cipher suites to secure your MQTT channels and client apps. However, SHA-2 cipher suites are not enabled by default until Java 7 from IBM, SR4 onwards, so in earlier versions you must specify the required suite. If you are running an MQTT client with your own JRE, you need to ensure that it supports the SHA-2 cipher suites. For your client apps to use SHA-2 cipher suites, the client must also set the SSL context to a value that supports Transport Layer Security (TLS) version 1.2.
Restrictions in browser support for mobile messaging web apps over SSL
There are differences in capability between different browsers, on different platforms. Understanding these differences helps you configure your apps, certificate authorities (CAs) and client certificates to connect using the MQTT messaging client for JavaScript over SSL and WebSockets.
Resolving problem: MQTT client does not connect
Resolve the problem of an MQTT client program failing to connect to the telemetry (MQXR) service.
Resolving problem: MQTT client connection dropped
Find out what is causing a client to throw unexpected ConnectionLost exceptions after successfully connecting and running for either a short or long while.
Resolving problem: Lost messages in an MQTT application
Resolve the problem of losing a message. Is the message non-persistent, sent to the wrong place, or never sent? A wrongly coded client program might lose messages.
Resolving problem: Telemetry (MQXR) service does not start
Resolve the problem of the telemetry (MQXR) service failing to start. Check the WebSphere MQ Telemetry installation and no files are missing, moved, or have the wrong permissions. Check the paths used by the telemetry (MQXR) service locate the telemetry (MQXR) service programs.
Resolving problem: JAAS login module not called by the telemetry service
Find out if your JAAS login module is not being called by the telemetry (MQXR) service, and configure JAAS to correct the problem.
Resolving problem: Starting or running the daemon
Consult the IBM WebSphere MQ Telemetry daemon for devices console log, turn on tracing, or use the symptom table in this topic to troubleshoot problems with the daemon.
Resolving problem: MQTT clients not connecting to the daemon
Clients are not connecting to the daemon, or the daemon is not connecting to other daemons or to a WebSphere MQ telemetry channel.

Parent topic: Introduction to MQTT

Related tasks

Tracing and debugging the MQTT (Paho) Java client
Tracing the MQTT JavaScript client
Tracing the telemetry (MQXR) service
Tracing the MQTT v3 Java client
Tracing the MQTT client for C
Resolving problem: MQTT client does not connect
Resolving problem: MQTT client connection dropped
Resolving problem: Lost messages in an MQTT application
Resolving problem: Telemetry (MQXR) service does not start
Resolving problem: JAAS login module not called by the telemetry service
Resolving problem: Starting or running the daemon
Resolving problem: MQTT clients not connecting to the daemon

Related reference

Location of telemetry logs, error logs, and configuration files
MQTT v3 Java client reason codes
System requirements for using SHA-2 cipher suites with MQTT clients
Restrictions in browser support for mobile messaging web apps over SSL