With Serial I could not see the output. I am using Dragino MS14-P with M32W. Console is compatible with Serial, so I replaced it and the output is visible to the Serial Monitor of Arduino IDE.
there was a problem with the curly brackets. Even when the whole string is tested on ssh at the Dragino, the curl had a problem with the curly brackets. -g parameter helped the curl process sends json data over GET to an external emoncms. This is the description of curl -g:

-g, --globoff

This option switches off the "URL globbing parser". When you set this option, you can specify URLs that contain the letters {}[] without having them being interpreted by curl itself. Note that these letters are not normal legal URL contents but they should be encoded according to the URI standard.