Flutter get return empty body but it is not empty - flutter

Question

as I wrote in the title I'm trying to obtain data from a server but the method http.get(Uri.parse(url)) returns empty body and od course the error caused by trying to decode an empty body,
But if I copy paste the url used before I can see the json content. How is it possible?
The function I'm using is:
Future getData ( ) async {
String url = 'http://www.viaggiatreno.it/viaggiatrenonew/resteasy/viaggiatreno/andamentoTreno/...';
http.Response response = await http.get(Uri.parse(url));
if (response.statusCode == 204) {
var data = response.body;
print("data are : $data");
return jsonDecode(data);
} else {
print("unable to load data");
}
}
This is a little portion of what I should see with this command: print("data are : $data");
{
"tipoTreno":"PG",
"orientamento":"B",
"codiceCliente":1,
"fermateSoppresse":[
],
"dataPartenza":null,
"fermate":[
{
"orientamento":"B",
"kcNumTreno":null,
"stazione":"VENEZIA SANTA LUCIA",
"id":"S02593",
"listaCorrispondenze":null,
"programmata":1646663160000,
"programmataZero":null,
"effettiva":1646663160000,
"ritardo":0,
"partenzaTeoricaZero":1646663160000,
"arrivoTeoricoZero":null,
"partenza_teorica":1646663160000,
"arrivo_teorico":null,
"isNextChanged":false,
"partenzaReale":1646663160000,
"arrivoReale":null,
"ritardoPartenza":0,
"ritardoArrivo":0,
"\"pro ...........}"
so as you can see the body is what you want but not empty, and it is in json format.
Can anyone help me? I can't solve this issue.
Output is:
I/flutter (3177): data are:
E/flutter ( 3177): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: FormatException: Unexpected end of input (at character 1)
E/flutter ( 3177):
E/flutter ( 3177): ^
E/flutter ( 3177):
E/flutter ( 3177): #0 _ChunkedJsonParser.fail (dart:convert-patch/convert_patch.dart:1405:5)
E/flutter ( 3177): #1 _ChunkedJsonParser.close (dart:convert-patch/convert_patch.dart:523:7)
E/flutter ( 3177): #2 _parseJson (dart:convert-patch/convert_patch.dart:41:10)
E/flutter ( 3177): #3 JsonDecoder.convert (dart:convert/json.dart:612:36)
E/flutter ( 3177): #4 JsonCodec.decode (dart:convert/json.dart:216:41)
E/flutter ( 3177): #5 jsonDecode (dart:convert/json.dart:155:10)
E/flutter ( 3177): #6 NetworkHelper.ottieniTutteInfo (package:agenda_ferrovia/utilities/networkConnection.dart:36:14)
E/flutter ( 3177): <asynchronous suspension>
E/flutter ( 3177): #7 _ServizioUIAggiungiTrenoState.build.ottieniOrigine (package:agenda_ferrovia/screens/servizioUI/servizioUI_singolo.dart:110:33)
E/flutter ( 3177): <asynchronous suspension>
E/flutter ( 3177): #8 _ServizioUIAggiungiTrenoState.build.<anonymous closure> (package:agenda_ferrovia/screens/servizioUI/servizioUI_singolo.dart:231:23)
E/flutter ( 3177): <asynchronous suspension>
E/flutter ( 3177):

Answer 1

Thanks all for the support! I've found the issue!
Some part of the 'url's String' comes from another call.
Inside a variable there was the "hidden chars" \n. That was the cause of the issue -.-
I've solved removing all chars except letters before save into variable used for the 'url'.
I hope that my English was clear enough to understand.
Bye!