Can't use GET HTTP request successfully

Projects Programming
1

Currently, I use ESP8266-V12 connect with Arduino Uno by UART. I want send data to server by using GET HTTP request via calling senddata(). And I want to get information from a file txt on server via pingrequest().
But, I can't GET successfully. Could you please review my code?
If code has any problem, please teach me.
Thanks

#include <SoftwareSerial.h>

SoftwareSerial esp8266(2, 3); 
void printResponse();
void setup_wifi();
char serialbuffer[100];//serial buffer for request url

void setup()  
{
  Serial.begin(9600);
  while (!Serial) {
  }
  esp8266.begin(9600); // or 115200 if your ESP can only communicate at that speed
  setup_wifi();
}

void printResponse() {
  while (esp8266.available()) {
    Serial.println(esp8266.readStringUntil('\n')); 
  }
}

boolean WaitForOK(long timeoutamount) {
  return WaitForResponse("OK", timeoutamount);
}

boolean WaitForReady(long timeoutamount) {
  return WaitForResponse("ready", timeoutamount);
}

boolean WaitForResponse(String response, long timeoutamount) {
  unsigned long timeout = millis() + timeoutamount;

  while (millis() <= timeout) {
    while (esp8266.available() > 0) {
      int len = esp8266.readBytesUntil('\n', serialbuffer, sizeof(serialbuffer));

      String message = String(serialbuffer).substring(0, len - 1);

      if (message == response) {
        return true;
      }
    }
  }

  return false;
}

void setup_wifi()
{
  Serial.println("setup wifi");
  pinMode(12,OUTPUT);
  digitalWrite(12, LOW);
  delay(1000);
  digitalWrite(12, HIGH);
  
  esp8266.println("AT+RST");
  if (WaitForReady(2000))
  {
    Serial.println("\tAT+RST ......successfully");
  }

  esp8266.println("AT+CWQAP");
  if (WaitForOK(1000))
  {
    Serial.println("\tAT+CWQAP ......successfully");
  }

  esp8266.println("AT+CWMODE=1");
  if (WaitForOK(1000))
  {
    Serial.println("\tAT+CWMODE=1 ......successfully");
  }

  esp8266.println("AT+CIPMUX=1");
  if (WaitForOK(1000))
  {
    Serial.println("\tAT+CIPMUX=1 ......successfully");
  }

  String WIFI_NAME = "Cuong868";
  String PASS = "0938021868";
  String cmd="AT+CWJAP=\""+ WIFI_NAME + "\",\""+ PASS + "\"";
  esp8266.println(cmd);
  if (WaitForOK(7000))
  {
    Serial.print("\t");
    Serial.print(cmd);
    Serial.println(" ......successfully");
  }
  
  esp8266.println("AT+CIFSR");
  if (WaitForOK(1000))
  {
    Serial.println("\tAT+CIFSR ......successfully");
  }
}

unsigned long lastTimeMillis = 0;
unsigned int ID = 000001;
float flat = 0;
float flon = 0;

void senddata()
{
  while(1)
  {
    esp8266.println("AT+CIPSTART=4,\"TCP\",\"198.54.115.236\",80");
    if (WaitForOK(5000))
    {
      Serial.println("AT+CIPSTART=\"TCP\",\"198.54.115.236\",80");
      break;
    }
  }

  String send_cmd="GET /hethongphancung/thaydoi.php?ma=";
  send_cmd.concat(String(ID));
  send_cmd.concat("&vido=");
  send_cmd.concat(String(flat));
  send_cmd.concat("&kinhdo=");
  send_cmd.concat(String(flon));
  send_cmd.concat("&trangthai=0");
  send_cmd.concat(" HTTP/1.1\r\n");
  send_cmd.concat("Host: www.thungrac.tk\r\n\r\n");
  //send_cmd.concat("Connection: close\r\n\r\n");
  Serial.println(send_cmd);
  esp8266.print("AT+CIPSEND=4," + String(send_cmd.length() + 4));
  delay(1000);
  printResponse();
  
  esp8266.print(send_cmd);
  delay(1000);
  printResponse();
  
  delay(1000);
  esp8266.println("AT+CIPCLOSE");
  WaitForOK(1000);
}

String location= "/thung-rac/000001.txt";
void pingrequest()
{
  while(1)
  {
    esp8266.println("AT+CIPSTART=4,\"TCP\",\"198.54.115.236\",80");
    if (WaitForOK(5000))
    {
      Serial.println("AT+CIPSTART=\"TCP\",\"198.54.115.236\",80");
      break;
    }
  }

  String send_cmd="GET ";
  send_cmd.concat(location);
  send_cmd.concat(" HTTP/1.1\r\n");
  send_cmd.concat("Host: www.thungrac.tk\r\n\r\n");
  //send_cmd.concat("Connection: close\r\n\r\n");
  
  Serial.println(send_cmd);
  esp8266.print("AT+CIPSEND=4," + String(send_cmd.length() + 4));
  delay(1000);
  printResponse();
  
  esp8266.print(send_cmd);
  delay(1000);
  printResponse();
  
  delay(1000);
  esp8266.println("AT+CIPCLOSE");
  WaitForOK(1000);
}
int flag = 0;
void loop() 
{
  if(flag == 0 )
  {
    senddata();
    pingrequest();
    flag = 1;
  }
}
2

Seems all rather completed.
Where did you get that code from?

3 
      String message = String(serialbuffer).substring(0, len - 1);

Piss away resources making a String out of a string. Then make a copy of part of that string, from the first character the last. Just so you don't have to use strcmp() to see if two strings match. I don't get it.