display data from Firebase on serial port - black diamonds with question mark

Hi,
I am just starting my adventure with Arduino.
I have a problem with displaying data from firebase on Serial Port. I want to do this firstly to check value of one of my variable called ‘switch’.
When I upload my program then in Serial window I see only black diamonds with question mark… I read that i must decode json before display but I do not have much expiernce in json data and I didn’t found any easy to understand example.

#include <ArduinoJson.h>
#include <Bridge.h>
#include <HttpClient.h>
#include <SPI.h>
#include <Ethernet.h>

void setup() {
pinMode(13, OUTPUT);
digitalWrite(13, LOW);
Bridge.begin();
digitalWrite(13, HIGH);
int index=0;
Serial.begin(9600);

while (!Serial); // wait for a serial connection
}

void loop() {
// Initialize the client library
HttpClient client;
// Make a HTTP request:
client.get(“https://myproject.firebaseio.com/switch.json?print=pretty”);

// if there are incoming bytes available
// from the server, read them and print them:
while (client.available()) {
char c = client.read();

Serial.println(c);
}
Serial.flush();

delay(5000);
}

What baud rate do you have set in the Serial Monitor app?

9600

When I paste "https://myproject.firebaseio.com/switch.json?print=pretty" in the address of the browser, I get "null". The Serial Monitor apparently does not understand how to display the symbol that corresponds to return value in the same was as the browser does.

no no , address https://project-6713801325997267474.firebaseio.com/switch.json?print=pretty , It is my first post on forum, sorry

the value is set to '1'

Is that a character '1' or a value 1?

What does

char s = 1;
Serial.print("s = ");
Serial.println(s);

print?

it's a value ,
blackdiamonds with question mark again

it's a value

So, if you want to store the value in a char, and have it print looking like a '1', add '0' to the value.

What does

char s = 1 + '0';
Serial.print("s = ");
Serial.println(s);

print?

still the same...

I have char in other variable :
https://project-6713801325997267474.firebaseio.com/-KJu2fDMafguIaAaxBtG.json
and also have black diamonds