Simple MQTT tools

Two applications are provided primarily to test the usage of the MQTT protocol and specifically BulletGCSS telemetry.

• mqttsub Subscribe to a MQTT service, display received data, optionally generate time-stamped log
• mqttplayer Replay a MQTT log (from mqttsub or BulletGCSS) to a MQTT server, preserving message timing.
• mqttcap Persistent subscription capture. mqttcap can be left running in the background and can capture MQTT data to distinct files in logdir from the broker subscription.

$ mqttsub --help
Usage of mqttsub -broker URI [options] ...
  -broker string
    	Mqtt URI (mqtt://[user[:pass]@]broker[:port]/topic[?cafile=file])
  -log string
    	log file for messages
  -qos int
    	The QoS for message subscription

$ mqttplayer --help
Usage of mqttplayer -broker URI [options] file
  -broker string
    	Mqtt URI (mqtt://[user[:pass]@]broker[:port]/topic[?cafile=file])
  -fast
    	Speed up x10
  -qos int
    	The QoS for message publication

$ mqttcap --help
Usage of mqttcap -broker URI [options] ...
  -broker string
    	Mqtt URI (mqtt://[user[:pass]@]broker[:port]/topic[?cafile=file])
  -logdir string
    	log directory for messages (default "/tmp")
  -splittime int
    	split time for logs (default 300)

Note that the scheme (mqtt:// in the --help text) is interpreted as:

• ws - Websocket (vice TCP socket), ensure the websocket port is also specificed
• wss - Encrypted websocket, ensure the TLS websocket port is also specificed. TLS validation is performed using the system CA files.
• mqtts - Secure (TLS) TCP connection. Ensure the TLS port is specified. TLS validation is performed using the system CA files.
• mqtt (or anyother scheme) - TCP connection. If ?cafile=file is specified, then that is used for TLS validation (and the TLS port should be specified).

Log file

The log file generated by mqttsub contains payload data, prefixed with a time_t-like timestamp with millsecond precision. The timestamp and payload are separated by a TAB character.

1611845402.129  cs:JRandomUAV,
1611845402.130  flt:0,ont:60,ran:20,pan:-10,hea:263,ggc:200,alt:0,asl:33,gsp:0,bpv:16.80,cad:0,cud:0.11,rsi:100,

As well as mqttsub log files, mqttplayer can also replay BulletGCSS log files. These are characterised by a millisecond Unix epoch timestamp, a '|' separator followed by the data.

if the log contains no timestamp and separator, the contents are replayed at 1 second interval.

Installation

Requires a Go compiler and make.

make

then copy mqttsub and mqttplayer somewhere convenient.