Error using thingspeak talk back to control arduino led - arduino

Question

The error I'm facing is about using talkback function of thingspeak to control my Arduino LED. it cannot execute the talkback command to off the led. The error is in my void get talkback. Please help me
#include "ThingSpeak.h"
#include <Ethernet.h>
#define redLED 8
byte mac[] = {0x90, 0xA2, 0xDA, 0x10, 0x40, 0x4F};
const String channelsAPIKey = "";
const String talkBackAPIKey = "";
const String talkBackID = "";
const String talkCommandID = "";
const unsigned int getTalkBackInterval = 10 * 1000;
const unsigned int updateChannelsInterval = 15 * 1000;
String talkBackCommand;
long lastConnectionTimeChannels = 0;
boolean lastConnectedChannels = false;
int failedCounterChannels = 0;
long lastConnectionTimeTalkBack = 0;
boolean lastConnectedTalkBack = false;
int failedCounterTalkBack = 0;
char charIn;
// Arduino Ethernet Client is initialized
EthernetClient client;
void setup()
{
Ethernet.init(10); // Most Arduino Ethernet hardware
Serial.begin(9600); //Initialize serial
// start the Ethernet connection:
pinMode(redLED, OUTPUT);
digitalWrite(redLED, HIGH);
}
void loop()
{
getTalkBack();
}
void getTalkBack()
{
String tsData;
tsData = talkBackID + "/commands/execute?api_key=" + talkBackAPIKey;
if ((!client.connected() && (millis() - lastConnectionTimeTalkBack > getTalkBackInterval)))
{
if (client.connect("api.thingspeak.com", 80))
{
client.println("GET /talkbacks/" + tsData + " HTTP/1.0");
client.println();
lastConnectionTimeTalkBack = millis();
if (client.connected())
{
Serial.println("---------------------------------------");
Serial.println("GET TalkBack command");
Serial.println();
Serial.println("Connecting to ThingSpeak");
Serial.println();
Serial.println();
Serial.println("Server response");
Serial.println();
failedCounterTalkBack = 0;
while (client.connected() && !client.available()) delay(2000); //waits for data
while (client.connected() || client.available())
{
charIn = client.read();
talkBackCommand += charIn;
Serial.print(charIn);
if (talkBackCommand == "LED_ON")
{
digitalWrite(redLED, HIGH);
}
if (talkBackCommand == "LED_OFF")
{
digitalWrite(redLED, LOW);
}
}
if (talkBackCommand = talkBackCommand.substring(talkBackCommand.indexOf("_CMD_") + 5));
{
Serial.println();
Serial.println();
Serial.println("Disconnected");
Serial.println();
Serial.println("--------");
Serial.println();
Serial.println("talkback command was");
Serial.println();
Serial.println("--------");
Serial.println();
Serial.println(talkBackCommand);
Serial.println("--------");
Serial.println();
}
}
else
{
failedCounterTalkBack++;
Serial.println("Connection to ThingSpeak failed (" + String(failedCounterTalkBack, DEC) + ")");
Serial.println();
lastConnectionTimeChannels = millis();
}
}
}
if (failedCounterTalkBack > 3 )
{
startEthernet();
}
client.stop();
Serial.flush();
}
The below is a image from my serial monitor. It shows that I can capture the command but couldn't execute it.

Answer 1

Looks like you are reading and appending all the received bytes to talkBackCommand. So, talkBackCommand is "HTTP/1.1 200 OK Date...." and if (talkBackCommand == "LED_ON") would never be true.
I think you wanted to see if the received data contain your commands LED_ON or LED_OFF. You can do something like this:
if (talkBackCommand.indexOf("LED_ON") != -1)
indexOf() locates a String in a String and returns index or -1 if not found.
See more info about indexOf() here: https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/indexof/