60 lines
1.7 KiB
Markdown
60 lines
1.7 KiB
Markdown
# System / `psmq` Publish Subscribe Message Queue
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`psmq` is publish subscribe message queue. It's a set of programs and libraries
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to implement publish/subscribe way of inter-process communication on top of
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POSIX message queue.
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Manuals, source code and more info at: https://psmq.kurwinet.pl
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Little demo using `psmqd` broker, `psmq_pub` and `psmq_sub`:
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Start broker and make it log to file
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```
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nsh> psmqd -b/brok -p/sd/psmqd/psmqd.log
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```
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Start subscribe thread that will read all messages send on `/can/*` topic
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```
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nsh> psmq_sub -n/sub -b/brok -t/can/* -o/sd/psmq-sub/can.log
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n/connected to broker /brok
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n/subscribed to /can/*
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n/start receiving data
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```
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Publish some messages
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```
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nsh> psmq_pub -b/brok -t/can/engine/rpm -m50
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nsh> psmq_pub -b/brok -t/adc/volt -m30
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nsh> psmq_pub -b/brok -t/can/room/10/temp -m23
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nsh> psmq_pub -b/brok -t/pwm/fan1/speed -m300
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```
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Check out subscribe thread logs
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```
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nsh> cat /sd/psmq-sub/can.log
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```
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```
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[1970-01-01 00:00:53] topic: /can/engine/rpm, priority: 0, paylen: 3, payload:
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[1970-01-01 00:00:53] 0x0000 35 30 00 50.
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[1970-01-01 00:00:58] topic: /can/room/10/temp, priority: 0, paylen: 3, payload:
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[1970-01-01 00:00:58] 0x0000 32 33 00 23.
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```
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As you can see `/adc/volt` and `/pwm/fan1/speed` haven't been received by
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subscribe thread.
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Content:
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- `psmqd` – broker, relays messages between clients.
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- `psmq_sub` – listens to specified topics, can be used as logger for
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communication (optional).
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- `psmq_pub` – publishes messages directly from shell. Can send binary data, but
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requires pipes, so on nuttx it can only send ASCII.
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- `libpsmq` – library used to communicate with the broker and send/receive
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messages.
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