This is just a guess, but it looks like you are sending it an empty string as the first object in your array
Have you tried it without an empty string as the first object?
Quote
"params": ["", "{\"1HwLtBDtLGeHrLkGWHKfE7WgbCz5FbdWW4\":0.0002, \"1G3kKtEK356sfkKaykQvnv37GFUPR3Lns4\":0.0002, \"1KigrTAFLRiZQuHEeX1TwfgzvijtvxU4WA\":0.0002}", 6, "testing"]
Have you tried it without an empty string as the first object?
Quote
"params": ["{\"1HwLtBDtLGeHrLkGWHKfE7WgbCz5FbdWW4\":0.0002, \"1G3kKtEK356sfkKaykQvnv37GFUPR3Lns4\":0.0002, \"1KigrTAFLRiZQuHEeX1TwfgzvijtvxU4WA\":0.0002}", 6, "testing"]
Tanks for the help.
The first object of the array is the name of the sending account. The empty string means the default account.
Anyway, I dropped the object and rerun the curl command, but this time the server did not even bother to answer an error (and the transaction was not sent).
Giving the same "sendall" command (with the empty string) directly as parameter of bitcoin-cli, however, works.
I am still in trouble.
Michele