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I am trying to get JSON data from my website using an HTTP GET request, but I'm getting a 400 bad request error. Can someone let me know why am I getting this error and how to fix that? I am tired of looking at online resources.

I am trying to fetch data from www.himalayavats.com/to_fetch/system_info.json

I am using this code:

#include <SoftwareSerial.h>

const byte rxPin = 2;
const byte txPin = 3;

SoftwareSerial ESP8266 (rxPin, txPin);

unsigned long lastTimeMillis = 0;

void setup() {
  sendData("AT+RST\r\n",1000, true);
  Serial.begin(9600);   
  ESP8266.begin(9600);
  delay(2000);
  connectToWifi();
}

void connectToWifi() {
  String ssid = "moto g";
  String pass = "hvats555";
  sendData("AT+CWMODE=1\r\n", 3000, true); // Configure as client
  sendData("AT+CWJAP=\"moto g\",\"hvats555\"\r\n", 5000, true);  // Connects to wifi
}

String sendData(String command, const int timeout, boolean debug) {
  String response = "";
  ESP8266.print(command); // send the read character to ESP8266
  long int time = millis();
  while( (time+timeout) > millis() ) {
    while(ESP8266.available()) {
      // The ESP has data so display its output to serial window
      char c = ESP8266.read(); // read the next character
      response+=c;
    }
  }
  if(debug) {
    Serial.print(response);
  }
  return response;
}

void printResponse() {
  while (ESP8266.available()) {
    Serial.println(ESP8266.readStringUntil('\n'));
  }
}

void loop() {
  if (millis() - lastTimeMillis > 30000) {
    lastTimeMillis = millis();
    ESP8266.println("AT+CIPMUX=1");
    delay(1000);
    printResponse();
    ESP8266.println("AT+CIPSTART=4,\"TCP\",\"himalayavats.com\", 80");
    delay(1000);
    printResponse();
    String cmd = "GET /to_fetch/system_info.json HTTP/1.1";
    ESP8266.println("AT+CIPSEND=4," + String(cmd.length() + 4));
    delay(1000);
    ESP8266.println(cmd);
    delay(1000);
    ESP8266.println("");
  }

  if (ESP8266.available()) {
    Serial.write(ESP8266.read());
  }
}

I get this response every time:

AT+CWMODE=1

OK
AT+CWJAP="moto g","hvats555"

WIFI DISCONNECT
WIFI CONNECTED
WIFI GOT IP

OK
AT+CIPMUX=1

OK

AT+CIPSTART=4,"TCP","himalayavats.com",80

4,CONNECT

OK

AT+CIPSEND=4,43

OK
> 
Recv 43 bytes

SEND OK

+IPD,4,1370:HTTP/1.1 400 Bad Request
Date: Tue, 19 Dec 2017 08:30:21 GMT
Server: Apache
Accept-Ranges: bytes
Vary: Accept-Encoding,User-Agent
Connection: close
Content-Type: text/html

My JSON file on the website looks like this:

{"power" : "high"}
  • Why are you putting delay(1000); between ESP8266.println(cmd); and ESP8266.println("");? That's bound to break things... – dda Dec 19 '17 at 8:55
  • @dda getting error on removing delay – Himalya vats Dec 19 '17 at 10:29
  • What kind of error? – dda Dec 19 '17 at 10:38
  • And anyway you should build your request so that the two CRLF are in the string, and send that. – dda Dec 19 '17 at 10:39
  • 2
    the delays are a substitute for waiting on confirmation from the esp. better use a library that makes the AT communication for you. for example the WiFiEsp library github.com/bportaluri/WiFiEsp – Juraj Dec 19 '17 at 10:50
2

Take a look at the HTTP specification:

Request       = Request-Line              ; Section 5.1
                *(( general-header        ; Section 4.5
                 | request-header         ; Section 5.3
                 | entity-header ) CRLF)  ; Section 7.1
                CRLF
                [ message-body ]          ; Section 4.3

Request-Line  = Method SP Request-URI SP HTTP-Version CRLF

You don't send the CRLF (carriage return, line feed) at the end of your request line and at the end of the header at the same time of the request. Why the delay?

You also miss the obligatory host header.

Host = "Host" ":" host [ ":" port ] ; Section 3.2.2
  • getting the error without delay AT+CWMODE=1 OK AT+CWJAP="moto g","hvats555" 4,CLOSED WIFI DISCONNECT WIFI CONNECTED WIFI GOT IP OK AT+CIPMUX=1 AT+CIPSTART=4,"TCP","himalayavats.com",80 busy GET /to_fetch/system_info.json HTTP/1.1 ERROR – Himalya vats Dec 19 '17 at 9:33

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