Struggling with exec node

General
1

I've been struggling to use the exec node to run a command that will work in a standard linux cli. The command sends a request to a thermostat in my home, and returns a JSON object with the current status of the thermostat. The command is:

echo -e '{"GET_SYSTEM": 0}\0\r' | nc 192.168.1.20 4242

It works perfectly in the Raspberry Pi terminal, but when I've tried using it in the exec node, I don't get the result I'd expect:

1 - If I add the command, as written above, to the "Command" field of the exec node, I get no message on the stdout, stderr or return code outputs of the node.

2 - I've tried changing to spawn mode, instead of exec node, and then I get a raw data buffer output, which I can't comprehend.

3 - I've tried "injecting" the command to the exec node as well, and this gives the same results.

Any pointers? Is there something obvious I'm missing?

2

can you show us the debug output of the spawn command - The node will try to parse it to a string - but if there are any non-ascii characters in there it will drop back to a buffer.

3

so you are actually running multiple commands because of the Piping. Try this, put the commands in a script then execute the script.

4

Hi @dceejay. Output using spawn mode (using the "copy value" button in the debug panel) looks like:

[39,123,34,71,69,84,95,83,89,83,84,69,77,34,58,32,48,125,0,13,39,32,124,32,110,99,32,49,57,50,46,49,54,56,46,52,46,50,52,48,32,52,50,52,50,10]

5

Hi @zenofmud. Do you mean, create a script file on the local filesystem, and trigger that from within node red?

6

that's just the command echo'd back :slight_smile:

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but yeah why not try the tcp request node as that seems to be what you are doing... just sending a tcp command to port 4242

7

Solved! One of those things I'm embarrassed I didn't spot. The netcat command wasn't automatically closing the server connection after receiving data. Adding a short timeout flag to the end of the command sorted everything. :slight_smile:

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8

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