ESP8266: HTTP GET Requests

The objective of this post is to explain how to perform GET Requests using the ESP8266.


Introduction

The objective of this post is to explain how to perform GET Requests using the ESP8266. If you prefer a video explanation, you can check my YouTube channel:

The tests were performed using a NodeMCU board, a very cheap and easy to use ESP8266 board.


Setup

First, we need do include some libraries. Naturally, we need the ESP8266WiFi library, which provides us the methods to connect to a WiFi network.

Then, we need the ESP8266HTTPClient library, which provides methods to send HTTP requests. The header file for the ESP8266HTTPClient library can be seen here.

#include <esp8266wifi.h>
#include <esp8266httpclient.h>

On the setup function, we connect to the WiFi Network. We also start a Serial connection for debugging. More details about how to connect to a WiFi network using the ESP8266 are explained in this previous post.

const char* ssid = "yourNetworkName";
const char* password = "yourNetworkPassword";

void setup () {

  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(1000);
    Serial.print("Connecting..");

  }

}


The main code

The code for the request will be specified in the main loop function. First, we declare an object of class HTTPClient, which we will simply call http. This class provides the methods to create and send the HTTP request.

HTTPClient http;

After that, we call the begin method on the http object and pass the URL that we want to connect to and make the GET request. The destination website specified here implements a dummy REST API for testing and prototyping.

http.begin("http://jsonplaceholder.typicode.com/users/1");

Then, we send the request by calling the GET method on the http object. This method will return the status of the operation, which is important to store for error handling. If the value is greater than 0, then it’s a standard HTTP code. If the value is less than 0, then it’s a client error, related with the connection. All available error codes for this method are listed here.

int httpCode = http.GET();

So, if the code is greater than 0, we can get and print the response payload, by calling the getString method on the http object.

String payload = http.getString();
Serial.println(payload);

Finally, we call the end method. This is very important to close the TCP connection and thus free the resources.

http.end();

The final complete code is shown bellow. You just need to put your network name and network password.

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>

const char* ssid = "yourNetworkName";
const char* password = "yourNetworkPassword";

void setup () {

  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(1000);
    Serial.print("Connecting..");

  }

}

void loop() {

  if (WiFi.status() == WL_CONNECTED) { //Check WiFi connection status

    HTTPClient http;  //Declare an object of class HTTPClient

    http.begin("http://jsonplaceholder.typicode.com/users/1");  //Specify request destination
    int httpCode = http.GET();                                                                  //Send the request

    if (httpCode > 0) { //Check the returning code

      String payload = http.getString();   //Get the request response payload
      Serial.println(payload);                     //Print the response payload

    }

    http.end();   //Close connection

  }

  delay(30000);    //Send a request every 30 seconds

}

The output of the program is shown in figure 1. The response corresponds to a JSON payload.

ESP8266 GET Request

Figure 1 – Output of the GET Request.

Finally, it’s important to take in consideration that the microcontroller has a limited amount of resources and thus it is not able to handle very large results. So, it is not expected that it will be used to make and process requests to sites that return a lot of information, as a typical browser would do.


Technical details

ESP8266 libraries: v2.3.0

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106 Responses to ESP8266: HTTP GET Requests

  1. Robert says:

    Thankssss a lot, i try everything, and this save me… You Rock!

    Liked by 1 person

  2. mauricio says:

    Budy, your code doesn’t shows me anything on Monitor Serial, what is happening?

    Liked by 1 person

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  4. Pingback: ESP8266: Posting JSON data to a Flask server on the cloud | techtutorialsx

  5. paolo kusanovic says:

    hi , can you list the entire code ? to this sample ?

    thanks

    Liked by 1 person

  6. gary says:

    Sir, Can i send a request per second?

    Liked by 1 person

    • antepher says:

      Hi, I never tried with that rate of requests but I think you can.
      What is your concern about that number of requests?

      Like

      • gary says:

        I would like to upload sensor readings to mysql via esp8266. I want to upload those readings per second. Is it possible? Thank you for your reply!

        Liked by 1 person

        • antepher says:

          Hi, I think there is no problem with sending a request per second. Nevertheless, if you need to guarantee that rate, maybe you should go to something a little more optimized, such as direct socket connection. That way, you don’t have the overhead of the HTTP protocol and the need to connect / disconnect each time you are sending a request. With the socket, you can leave it open while you need.

          I don’t know of a way to directly send the data to a SQL database using the ESP. The protocols used to access the DB are different, unless you can find a way to expose the database functionality directly over HTTP.

          So, for using the code shown here, the easiest way is to develop a server application (for example, in Python or Java) that receives the data from the ESP via HTTP and then inserts it on the MySQL database using a suitable protocol.

          Hope it helps

          Like

          • gary says:

            Thank you for your reply!
            I am using php to insert data into mysql. The process of sending a request is about 2 to 3 seconds. The is not what i want. Direct socket connection? How to use it?

            Like

            • antepher says:

              Hi!

              Sockets are lower level mechanisms to allow computers (and now, microcontrollers such as the ESP8266) to communicate through a network. So, HTTP is actually a protocol that works on top of socket communication. You can read a lot about sockets around the web, it’s a very well known and documented mechanism.

              I have no tutorial yet on how to use them, but in the libraries for the Arduino IDE there is a very nice example that you can adapt, for the ESP8266:
              https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266WiFi/examples/WiFiClient/WiFiClient.ino

              But please note that in the example they are building the HTTP protocol by hand, on top of the socket connection, which would have the same result. In your case, moving to socket oriented communication with increased performance would need some changes, both in the ESP code and the server, to keep the connection alive. Probably you may not want to do this kind of changes.

              In your case, it seems that you are having performance issues, maybe with the php server, which you can try to optimize in order to achieve the desired rate. Have you tried to make the request to your php page from other tool, just to confirm if you can do a request per second? That way you can confirm if the problem is on the ESP8266 side or on the php server side.

              Do you insert the data on the database synchronously? If so, you leave the ESP8266 waiting for the procedure to conclude, which takes some time. One approach could be returning an immediate response to the ESP and then inserting the data asynchronously.

              You can also try to measure the execution time of the different procedures you have in your php page, to check where it is taking more time and trying to optimize.

              Like

  7. Djovanni says:

    Hey, I have a working http request working, except what you don’t cover in this tutorial is the ability to use specific json data. I have been searching everywhere to achieve this, but without any results. Can you please help me how I would get the value of a json key, such as street name, and save it in a variable. Thanks in advance!

    Liked by 1 person

  8. djohalo2 says:

    Hey, I have a working http request working, except what you don’t cover in this tutorial is the ability to use specific json data. I have been searching everywhere to achieve this, but without any results. Can you please help me how I would get the value of a json key, such as street name, and save it in a variable. Thanks in advance!

    Liked by 1 person

  9. antepher says:

    Hi!

    You can check this previous tutorial on how to parse JSON content on the ESP8266. You can use it to parse incoming JSON content, as a result of your request:
    https://techtutorialsx.com/2016/07/30/esp8266-parsing-json/

    Here is a more advanced tutorial, were is explained how to parse JSON arrays:
    https://techtutorialsx.com/2016/08/06/esp8266-parse-json-arrays/

    In case you need it in the future, here is explained how to encode JSON messages in the ESP8266. You can used to POST content in JSON format:
    https://techtutorialsx.com/2016/08/10/esp8266-encoding-json-messages/

    Please let me know if it helps. Also, let me know if you get any compiling errors. I’ve been changing the aspect of the coding sections of those posts and sometimes WordPress removes stuff between less than and greater than signals, which may cause unexpected errors, such as loosing includes.

    Like

  10. jonbuch says:

    Hi. we are having trouble getting this to work. We get the
    /// HTTP client errors
    #define HTTPC_ERROR_CONNECTION_REFUSED (-1)
    when running. It seems this occur when we change your json link to our link which is an ifttt trigger (you can check it here: https://maker.ifttt.com/use/DVoJmf_Gobw7RJMLguWUy ). Any idea for fixing this?

    Liked by 1 person

    • antepher says:

      Hi!

      I think the error may be related to the fact that the website you are trying to reach uses HTTPS. This is a secure version of the HTTP protocol and it means that the connections are encrypted.

      The example shown in this tutorial works only for HTTP (the not secure version where the data is sent in plain text)

      I haven’t yet played with HTTPS in the ESP8266, but you have here an example, from the ESP libraries:
      https://github.com/esp8266/Arduino/blob/master/libraries/ESP8266WiFi/examples/HTTPSRequest/HTTPSRequest.ino

      Note that in that example the fingerprint of the digital certificate of the website you are trying to reach is hardcoded. If the digital certificate of the website expires, then the code will stop working.

      In real world HTTPS, the client validates the digital certificate of the website (typically your browser is the client) to check if that certificate can be trusted. This is done by contacting a chain of certificate authorities.

      This is a heavy process that would not be trivial to implement in a device with limited resources, such as the ESP8266. I haven’t yet found a library that does this efficiently. Maybe with the new ESP32 this will be easier to implement

      Nevertheless, you can follow the thread about SSL support for the ESP8266 on the github page of the ESP libraries for the Arduino IDE. I opened the issue 2 years ago 🙂
      https://github.com/esp8266/Arduino/issues/43

      Liked by 1 person

  11. Cao Zhelin says:

    Hi, I tried your code, but my monitor show things like this:
    ———————————————————————————–
    Connecting..
    Connecting..
    Connecting..
    200 // httpCode

    ——————————————————————————————
    My payload is strange, do you know what’s the problem?

    Liked by 1 person

  12. Cao Zhelin says:

    html
    head
    meta http-equiv=’refresh’ content=’1; url=http://jsonplaceholder.typicode.com/users/3&arubalp=91c4147b-74cb-4485-8af4-a79f9975fc’
    /head
    /html

    Like

    • Cao Zhelin says:

      finally… I removed all the, but the payload is like this.

      Like

      • antepher says:

        Hi! If you are trying to paste HTML tags WordPress won’t allow you, sorry. I think it is due to security reasons.

        Are you making the post request to this exact URL?
        http://jsonplaceholder.typicode.com/users/1

        Can you please copy and paste the URL in your browser just to confirm you are receiving the JSON payload?

        Like

        • Cao Zhelin says:

          My browser can receive the payload correctly as shown in the tutorial.The problem is my ESP8266, My URL is correct but my ESP8266 still prints the HTML tags as payload(not the texts my browser shows). I don’t know why.

          Like

        • Cao Zhelin says:

          I looked up the returned tag inform me to refresh into a new URL below in 1 second:

          http://jsonplaceholder.typicode.com/users/3&arubalp=91c4147b-74cb-4485-8af4-a79f9975fc

          The page above is empty. So I do receive response from the test page, and the response tells me get into anther empty page, why is that?

          Like

        • Cao Zhelin says:

          After refreshing to the new URL, my httpCode change to 302(redirect), with no payload, I currently stuck at here, don’t know how to response to httpCode 302

          Like

          • antepher says:

            Hi! That’s really weird, I’ve just copied and pasted the code on my IDE and uploaded it to a ESP8266 NodeMCU board and it works just fine.

            Can you please tell me which version of the Arduino libraries are you using? Can you please also paste the main loop function here?

            Maybe there is a problem with the character encoding or something with the Arduino IDE. May I ask in what language is your IDE? I never faced a problem like this but if you are copying and pasting the code without success, there may be something with the URL characters.

            Can you send requests to other websites?

            Like

            • Cao Zhelin says:

              I finally solve the problem… that all because I connected to a network that is not working, I change another available WiFi and everything just works perfectly. Thanks for helping me with this somehow silly problem 🙂

              Liked by 1 person

  13. kbinumathew says:

    Hi, I would like to control a LED based on the contents of a google document. I need to read that file- which is basically a single line file. I tried your code and it is working fine. Now the problem is how to get that json parsing line (“http://jsonplaceholder.typicode.com/users/1”). I searched a lot, but in vain. Can you please help me..

    Liked by 1 person

  14. akarnib says:

    Hello
    I just have a small question. How will the code identify the connected pins of the ESP8266 to the Arduino board?

    Liked by 1 person

    • antepher says:

      Hi!

      I’m sorry I’m not sure if I understood your question. In this code we don’t use any digital pins of the board.

      If you are asking about using the ESP8266 in the Arduino IDE, then it is done for us in the background, we don’t need to worry about the details. Basically, the Arduino IDE will know that the code is being compiled for the ESP8266, and use the correct compiler / set of tools needed.

      This code was designed to work in a ESP8266 board, not in a Arduino one.

      Hope it answers your question. If not, please let me know.

      Like

      • akarnib says:

        Yes it did thank you a lot. I mixed it up for I am using the ESP8266 WiFi module connected to an Arduino UNO board. Speaking of which, I stumbled trying to send a GET request but I’m out of luck. It doesn’t seem to work and I’ve tried and searched through many links.
        I successfully connected to a website using “AT+CIPSTART” command but after that I can’t figure out exactly what needs to be done. I used the “AT+CIPSEND=” but I can’t really tell the exact structure of the GET request string before getting its length. I am really sorry I know my problem became off topic with respect to your post but I’m desperate for help and would highly appreciate it.

        Liked by 1 person

        • antepher says:

          No problem, let me see if I can help 🙂

          First of all, what you are seeing here is code for the ESP8266 and not for the Arduino boards, as I’ve mentioned.

          Nevertheless, we are using the Arduino development environment because Ivan Grokhotkov started a project to support the ESP8266 development on the Arduino IDE that has grown a lot with the support of the community. So, we don’t need to worry about setting complicated toolchains and we can use the Arduino language / development environment we are used to, in order to program the ESP8266.

          So, if you want to start programming your ESP8266 from scratch instead of using the pre-loaded AT commands firmware you are using, please consult the tutorial bellow. Just take in consideration that if you upload a program to the ESP8266, the AT commands firmware will be erased.
          https://techtutorialsx.com/2016/02/28/esp8266-uploading-code-from-arduino-ide/

          I really recommend that approach since you will have much more control of your programs and you can develop them to suit your needs.

          I used the AT commands firmware a couple of years ago, when the ESP8266 was still being sold as a Arduino serial to Wifi adapter and we didn’t now it was a fully programmable microcontroller. At that time, the firmware was considerably unstable and so I moved to the Arduino environment, as many others did.

          I only recently used the firmware again to do some tests on a board and I think its much more stable, but I still prefer to develop under the Arduino environment or other, such as mycropython.

          Hope I have convinced you to change to another environment 🙂 but if not, I think the best way is that you build the HTTP request string in a variable and simply get the size with the function bellow:
          https://www.arduino.cc/en/Reference/StringLength

          You will need to figure out the structure of the whole HTTP request for the site you are trying to reach, put it into a string and then getting the length. If your request is dynamic, you will need to build the string with the different parts and then get the size in the end.

          Note that what the firmware is doing with the AT commands is establishing a socket connection with the server, and you are going to need to send the whole HTTP request on top of that.

          Also, take in consideration that we cannot connect to HTTPS websites, because of the encryption.

          Like

          • akar says:

            Hello again and thanks for your effort in replying.
            I am actually trying to send the http GET request manually through writing the AT commands directly onto the serial monitor before moving to code. Testing wise I found it better this way before
            the implementation of the code. All respective commands for ESP8266-01 – Website communication are done successfully except for the GET request part.
            The first link you put is good in case I am using the ESP8266-01 module as a generic board, but I am not. Actually it’s connected to the RX TX of the Arduino UNO board along with other sensors and components.
            I took the length of the GET request now what remains is actually sending it but once I receive the “>” sign on the serial monitor, I enter the request but it disappears (it doesn’t appear on the monitor when I hit enter) and though it shows “SEND OK” it still did not send anything (the path of the link is a tested PHP script that adds a value to a database).
            Thanks for your advice but unfortunately I’m still out of luck. The website I’m trying to the send the request to is also not encrypted.

            Liked by 1 person

            • antepher says:

              Hi! As for the link, as long as you can program the ESP8266, you can develop the architecture of the system as you want. The only difference is that instead of using a pre-built firmware, you develop your own program for the ESP. You can still develop a program to receive data from an Arduino Uno, connect to a website, send the data, receive the response and send it back to the Arduino, I did something similar in a smart medication dispenser I built some time ago, where the Arduino Mega was running all the sensors and the ESP was just dealing with the communication. Nevertheless, I developed a custom program from the ESP, for more control.

              As for your problem with the AT command, maybe it is related with the delay between you sending the CIPSEND command, receive the “>” and then sending the actual data. I used the firmware a long ago for socket connections, but I have a slight idea of facing some problems with the command on the serial monitor.

              Other thing, are you sending the \r\n at the end of the actual data? It may be also needed and also accounted in the size of the content passed to the CIPSEND.

              Also, just for debugging, have you tried to send the command to other website, just for checking if something happens?

              I’ve been also searching for some libraries for the Arduino and I think you can use one similar to the shown bellow to interact with the ESP8266. It hides some of the AT commands details and probably guarantees the synchronization of the send command.
              https://github.com/itead/ITEADLIB_Arduino_WeeESP8266

              Like

  15. akar says:

    I think my problem is with the ESP8266-01 module itself. I bought 2 so far and couldn’t get them to work. I tried literally everything but the modules I have aren’t of good quality they started lagging and not always they were able to recognize the DNS. My friends are working with the ESP8266 NodeMCU board and I’m thinking of getting one. What’s your opinion? And also does this post should (if not must) work with that latter board right?

    Thank you for your time and help. I am probably switching hardware and thanks for convincing me! (if that’s what you meant earlier by changing to another environment).

    Liked by 1 person

    • antepher says:

      Just to clarify a thing, both the ESP8266-01 and the NodeMCU use the same microcontroller, the ESP8266. Those are just different boards built around the same microcontroller.

      So, all the code you see in my blog in the “ESP8266” category should work fine in any of them. Naturally, there may be a detail or another, but I try to leave a warning when we need to consider something additional specific to a certain board.

      The NodeMCU is a very good board and I have been using it for most of my posts on the ESP8266. The advantage is that it already has an USB header and you just need an USB cable to interact with it, which includes programming it.

      Besides that, it has all of the pins of the ESP8266 exposed, so you can use it as an “arduino”. Many people use the ESP8266 just as a Serial to WiFi converter, but the ESP8266 is actually much more powerful than most of the microcontrollers used in the Arduino boards. Most of the things you can do with an Arduino board you can do with an ESP8266 board, with the advantage of having WiFi built in.

      I think it is a very good option for you to move to the NodeMCU, but I also recommend you to program it with the Arduino IDE instead of using the AT commands. That’s what I meant when recommending you to change the environment 🙂 The AT commands have always been a little unstable and you typically end up with a more complex program because you need to be parsing strings from the answers of the commands.

      The link I shared before with the tutorial to move to the Arduino IDE covers the ESP-01 as hardware because at the time I wrote it it was the most used board. Now with the NodeMCU boards, we really just need an USB cable to connect it to a computer.

      Nevertheless, from the Arduino IDE Configuration section bellow are the generic instructions for installing the ESP8266 support for the Arduino IDE. You will only need to choose the correct board on the boards manager (in your case it will be the NodeMCU) because the upload configurations may vary from board to board. But the IDE takes care of everything as long as we choose the correct board.
      https://techtutorialsx.com/2016/02/28/esp8266-uploading-code-from-arduino-ide/

      I think it’s still working fine, but the latest instructions from the creators of the ESP8266 libraries for the Arduino IDE are bellow, if you prefer:
      https://github.com/esp8266/Arduino#installing-with-boards-manager

      Let me know if you succeed with the NodeMCU 🙂

      Like

      • akar says:

        Actually I’ve managed to solve my issue thanks to your advice (really this time). Approaching it by code, the http GET request was sent correctly. I thought it’s a ESP8266-01 since I followed several tutorials that used AT commands and successfully sent a request but mine did not. Eventhough I tried several Arduino IDE approaches (by code) I wasn’t successful at first until now

        Still, I will get a NodeMCU just as a backup plan and I will follow your instructions. Thanks a lot if it wasn’t for you I would’ve have gave it another try with the Arduino IDE.

        Here’s the link that I followed http://blog.huntgang.com/2015/01/20/arduino-esp8266-tutorial-web-server-monitor-example/#comment-5758

        Now that remains is that I need to get the response from the ESP-01 and type it again just to keep track in front of me of what’s happening. That link was great but it didn’t get back the responses.. I guess this is my next step. Thanks again for your assistance mate.

        Liked by 1 person

        • akar says:

          I thought it’s a ESP8266-01 problem***…

          Liked by 1 person

        • antepher says:

          You’re welcome, I’m glad it is working fine 🙂 I think you will like the NodeMCU, it’s much more easy to use than the ESP-01.

          Also, if you like Internet of Things, keep an eye for the ESP32 boards, it’s the ESP8266 big brother and it’s much much more powerful. 🙂

          Good luck with your project!

          Like

  16. Burak says:

    Thank you so much. It helped me so much to understand this ESP8266 beast. 🙂 Such blogs really help people like me who try to learn something without programming background and proceed with their enthusiasm.

    Once again. thanks a lot. much appreciated.

    Liked by 1 person

    • antepher says:

      Thank you very much for your feedback 🙂 It’s important for me to know that you are finding the content useful and easy to understand.

      Best regards,
      Nuno Santos

      Like

  17. Kay says:

    Hi,
    Firstly, I wanna commend you on this great post. I’ve been working on something similar but not entirely. I’m using an arduino, esp8266 and some sensors. the aim is to send data from the sensors to a server (not to a jsoplaceholder). I got it right when I’M sending data to a thingspeak channel (through an example code of course!)

    SoftwareSerial SerialS(8, 9) ;
    #include "ESP8266.h"
    ESP8266 wifi(SerialS,9600);
    
    

    The library I used was from ITEAD, and not your prescribed library in your tutorial,

    #define SSID "AndroidAP"      //name of wireless access point to connect to
    #define PASSWORD "*******"  //wifi password
    #define IP "184.106.153.149"                  
    
    
    String GET_start = "GET /update?key=";
    String writeAPIKey = "D*************SJ";    
    String GET_end1 =  "&field1=";                 // field1 for the Celcius
    String GET_end2 =  "&field2=";                 // field2 for the fahrenheit
    String GET_end3 =  "&field3=";
    String GET_end4 =  "&field4=";
    String GET_end5 =  "&field5=";
    
    String GET = GET_start + writeAPIKey + GET_end1 ;
    
    

    Here is one challenge I will be facing, the write API key is what I can’t substitute because heroku doesn’t have one.
    below is the remainder of the code for the sending of strings to the thingspeak server

        char buffer1[10];
        char buffer2[10];
        char buffer3[10];
        char buffer4 [10];
        char buffer5 [10];
        String light = dtostrf(ldr, 4, 1, buffer1);
        String voltBatt = dtostrf(vin1, 4, 1, buffer2);
        String voltSolar = dtostrf(vin2, 4, 1, buffer3);
        String hum = dtostrf(h, 4, 1, buffer4);
        String temp = dtostrf(t, 4, 1, buffer5);
        updateTemp(light,voltBatt,voltSolar,hum,temp);
    }
    
    void updateTemp(String temp1, String temp2, String temp3, String temp4, String temp5 ){
    
       if (wifi.createTCP(IP, (80))) {
         //   Display.print("create tcp ok \r\n");
         //Display.print(field);
        } else {
         //   Display.print("create tcp err\r\n");
        }
    
      String cmd = GET;
      cmd += temp1;
      cmd += GET_end2;
      cmd += temp2;
      cmd += GET_end3;
      cmd += temp3;
      cmd += GET_end4;
      cmd += temp4;
      cmd += GET_end5;
      cmd += temp5;
      cmd += "\r\n";
    
      ESPserial.print("AT+CIPSEND=");
      ESPserial.println(cmd.length());
      if(ESPserial.find(">")){
        Serial.print(">");
        Serial.print(cmd);
        ESPserial.print(cmd);
      }
    
      if(ESPserial.find("OK")){
        Serial.println("RECEIVED: OK");
      }else{
        Serial.println("RECEIVED: Error");
      }
    
      if (wifi.releaseTCP()) {
        //Display.print("release tcp ok \r\n");
      } else {
        //Display.print("release tcp err\r\n");
      }
    }
    
    

    But now, I have deployed on heroku and used firebase as my database server, and I want to make this code send my sensor data to my deployed server. Do you have any solution you can help me with? I’ll be forever grateful. Thanks!

    Kay.

    Liked by 1 person

    • antepher says:

      Hi! Thanks for your feedback, I’m glad you found this post useful 🙂

      As for your application, I haven’t yet worked with Heroku (although I definitely want to take a look as soon as I have some time), but I’m assuming you are deploying an application there with a endpoint that will receive your sensor data, right?

      First of all, you need to confirm that you are not using HTTPS on your application, if so you will not be able to send the data because of the encryption. So, you will need to be using just HTTP.

      I haven’t used ITEAD’s library, so I can’t be of much help in that part, but from what I’m seeing it is using AT commands.

      So, my suggestion is more of on how to approach the problem. Since you’re moving to a new platform, you should start by doing something really simple before sending the sensor data, in order to be able to debug.

      So, my recommendation is that you put a simple route in your Heroku app that just does something as simple as returning a “hello world” string. Thus, you can confirm that you can reach the server and send an HTTP request and get the answer.

      So, your command would be something like
      String GET = “GET /hello\r\n”;

      If you can reach the server like this, then you can build the remaining application on top of it. After that, you could do a route that receives your parameters as query strings, like you are doing in that code in the /update. First you can try if it works with your browser, and then move to the ESP/Arduino code.

      From my understanding of your code / application, if you set a /update route similar to the one you have on ThingsSpeak, you just need to remove the ?key= from the Get_start variable and in the following line of code remove the + writeAPIKey.

      String GET = GET_start + writeAPIKey + GET_end1 ;

      It would then be:
      String GET_start = “GET /update”;
      String GET_end1 = “?field1=”;
      (…)
      String GET = GET_start + GET_end1 ;
      (…)

      But you should test sending the request from a browser first to avoid having complicated debugging on the Arduino / ESP. If the problem is in the server, you need to solve it first.

      So, the bottom line is that if your backend doesn’t need an API key, you just don’t need to send one. Just send the remaining query parameters.

      Also, if you are not familiarized with why you are sending the ?field1=something&field2=something… do a quick search about how query parameters work. It’s very important to understand your code.

      Basically, it is a way for sending parameters to the server on the URL. In the code you are showing me, you can do the same request to ThingsSpeak from a web browser by typing the following on the search bar:

      http://184.106.153.149/update?key=YourAPIKey&field1=YourFieldValue&field2=YourFieldValue

      and so on for the remaining values (all in the same line).

      Hope it helps!

      Like

  18. Guilherme Lionco says:

    Thank you so much. I didn’t find a solution for my problem in another site, but your post helped me. Best Regards.

    Liked by 1 person

    • antepher says:

      Hi! Thank you very much for your feedback 🙂 I’m glad these posts are being useful, I will try to keep posting more content about the ESP8266.

      Best regards,
      Nuno Santos

      Like

  19. Maddy says:

    Hi Antepher, Your post is very useful for newcomers like me……….My problem is I don’t know whether I can use this library with ESP01 serial wifi transceiver SO I wanted to know can I use this library that you prescribed with ESP-01? If yes than How should I connect ESP01 to My arduino Mega? I am trying to send data to mySQL server it’s an RFID based logging system so I need to read the confirmation echo back from the server too….please guide me on that…..thank you

    Liked by 1 person

    • antepher says:

      Hi! Thanks for your feedback 🙂 Yes, you should be able to use it with the ESP01.

      These tutorials are for the ESP8266 microcontroller, which is found at those ESPXX boards (and many others).

      So, in theory, it should work as long as the microcontroller is the ESP8266, as it is the case of the ESP01.

      Naturally, in other programs where we use specific pins of the ESP8266, they may not be exposed in some boards, so you need to be careful with that. In this case we don’t use any GPIO.

      For the ESP01, you can check the tutorial bellow on how to program it with the Arduino IDE:
      https://techtutorialsx.com/2016/02/28/esp8266-uploading-code-from-arduino-ide/

      It’s a bit old, but I think it still applies to the ESP01. I can’t confirm since I’ve not been using the ESP01’s for a while. Due to the relatively complicated process of uploading code to the ESP01, I’ve started using other simpler to program ESP8266 boards.

      Let me know if it works.

      Best regards,
      Nuno Santos

      Like

  20. Rodolfo says:

    Hi, sorry about the dumb question but does this work with arduino uno board, or is it ESP8266 on its own?

    thanks

    Liked by 1 person

    • antepher says:

      Hi! It’s not a dumb question, many people have the same doubt 🙂

      This is the ESP8266 on its own, you don’t need an Arduino uno board or any other board.

      Although in the beginning, the ESP8266 was sold as an Arduino WiFi to serial bridge, the community quickly discovered that it was actually a very powerful microcontroller with WiFi support that could be programmed and used without any additional board.

      So, one of the projects that was first initiated was adding support on the Arduino IDE to program it. This was an awesome initiative since the original set of tools was very complicated and the Arduino was a well known environment for the community.

      So, to sum up, you just need an ESP8266 board (there are plenty of them on the market with usb headers for programming without external hardware) and the Arduino IDE and you can follow this tutorial.

      Hope this clarifies your doubt.

      Best regards,
      Nuno Santos

      Like

  21. reza says:

    hi,It’s not work for me
    see this: http://uupload.ir/files/4qjb_new_bitmap_image.bmp
    what can i do?

    Liked by 1 person

    • antepher says:

      Hi! Can you please share a description of the problem you are experiencing? Due to security reasons, I usually don’t follow links to uploaded files, hope you understand.

      Best regards,
      Nuno Santos

      Like

      • Masoud says:

        Hi, I have a same problem to. baud rate is ok but I can not see the data correctly. data in serial monitor is some thing like this : #?# . what is the problem ? note that I use the same URL as yours and some other URL but results are the same.

        Liked by 1 person

        • antepher says:

          Hi!

          That’s weird, I’ve not been able to reproduce the issue.

          Maybe some problem with your units or cable? Or are you able to do regular serial prints of string without any problem?

          Best regards,
          Nuno Santos

          Like

          • Masoud says:

            Yes, I am able to print Strings in serial monitor without any problem!! but when I use http.getString() I have problems in printing on serial monitor. note that I found a solution for my problem. I changed my access point and every thing is ok now! That’s so weird, do you have any idea about it? what is the problem of my old Access Point? it was a regular 4G/LTE TP-Link router!

            Liked by 1 person

            • antepher says:

              Hi!

              That’s really weird, I’ve never experienced that type of problem. Nonetheless, I’ve always used the ESP with my Thomson router.

              But I’m glad you were able to solve it. 🙂

              My suggestion is that you post your issue in the Git Hub page of the Arduino core, maybe someone there has faced the same issue and has a solution or ideia about the cause.

              Best regards,
              Nuno Santos

              Like

  22. veejien says:

    Neat work, crisp & clear!

    Liked by 1 person

  23. ejri says:

    Hello!
    I have tried running your code on a private network, and it works. However, whenever I use a public network, I get the following error.

    Connecting..Connecting..Connecting..
    Stylesheet for Squid Error pages
    Adapted from design by Free CSS Templates
    http://www.freecsstemplates.org
    Released for free under a Creative Commons Attribution 2.5 License
    */

    /* Page basics */
    * {
    font-family: verdana, sans-serif;
    }

    html body {
    margin: 0;
    padding: 0;
    background: #efefef;
    font-size: 12px;
    color: #1e1e1e;
    }

    /* Page displayed title area */
    #titles {
    margin-left: 15px;
    padding: 10px;
    padding-left: 100px;
    background: url(‘http://www.squid-cache.org/Artwork/SN.png’) no-repeat left;
    }

    /* initial title */
    #titles h1 {
    color: #000000;
    }
    #titles h2 {
    color: #000000;
    }

    /* special event: FTP success page titles */
    #titles ftpsuccess {
    background-color:#00ff00;
    width:100%;
    }

    /* Page displayed body content area */
    #content {
    padding: 10px;
    background: #ffffff;
    }

    /* General text */
    p {
    }

    /* error brief description */
    #error p {
    }

    /* some data which may have caused the problem */
    #data {
    }

    /* the error message received from the system or other software */
    #sysmsg {
    }

    pre {
    font-family:sans-serif;
    }

    /* special event: FTP / Gopher directory listing */
    #dirmsg {
    font-family: courier;
    color: black;
    font-size: 10pt;
    }
    #dirlisting {
    margin-left: 2%;
    margin-right: 2%;
    }
    #dirlisting tr.entry td.icon,td.filename,td.size,td.date {
    border-bottom: groove;
    }
    #dirlisting td.size {
    width: 50px;
    text-align: right;
    padding-right: 5px;
    }

    /* horizontal lines */
    hr {
    margin: 0;
    }

    /* page displayed footer area */
    #footer {
    font-size: 9px;
    padding-left: 10px;
    }
    body :lang(fa) { direction: rtl; font-size: 100%; font-family: Tahoma, Roya, sans-serif; float: right; } :lang(he) { direction: rtl; } –> ERROR The requested URL could not be retrieved The following error was encountered while trying to retrieve the URL: http://jsonplaceholder.typicode.com/users/1

    ICAP protocol error.

    The system returned: [No Error] This means that some aspect of the ICAP communication failed. Some possible problems are: The ICAP server is not reachable. An Illegal response was received from the ICAP server. Generated Sun, 24 Sep 2017 01:23:48 GMT by px019.st.vc.core.wifi.inet (squid/3.1.23)
    ERROR: The requested URL could not be retrieved <!– /*

    Like

    • antepher says:

      Hi! It seems like the public network you are trying to use has some kind of authentication page that you have to fill, and by trying to connect using the ESP library it is giving you some error. That HTML you are seeing is most likely an error page.

      If you try to connect to that network from your computer, don’t you need to fill a form or something similar on your browser?

      Like

      • ejri says:

        Hi! Thank you for the reply!

        Yes, an authentication is required. However, there’s an option to register the devices’ MAC addresses so that there is no need to authenticate. So, is it possible that the devices’ MAC addresses are wrong or not being supported (btw raspberry pi’s seem to work just fine..)? Are there any other suggestions? Is there a way to connect then authenticate using the ESP library without having to register the MAC address for example?

        Liked by 1 person

  24. Martin says:

    Hi there,
    first of all, thanks for the tutorial, it is great.
    Based on it, I have my own code and it works flawlessly. The problem is that the code wont start when I power the bord on. I need to connect to it through serial and then it works like a charm, but again, if i powercycle, nothing happens unless I start putty and connect to it again.
    Do you know what to do with it? My code has the same structure. consts, setup and loop as in your tutorial
    My board is https://www.banggood.com/NodeMcu-Lua-WIFI-Internet-Things-Development-Board-Based-ESP8266-CP2102-Wireless-Module-p-1097112.html?rmmds=myorder
    Geekcreit® NodeMcu Lua WIFI Internet Things Development Board Based ESP8266 CP2102 Wireless Module

    Thanks for help!

    Liked by 1 person

    • Martin says:

      My bad, its not that it was not working, there was a wire loose, while i transported it

      Liked by 1 person

      • antepher says:

        Hi Martin! Thanks for the feedback 🙂

        I’m glad you were able to solve the issue.

        Through my time in embedded systems development, I’ve also spent a fair amount of time looking for issues in the software that were actually being caused by hardware problems. 🙂

        Best regards,
        Nuno Santos

        Like

  25. Linh Tran says:

    Please take a look at my error. I don’t know where the problem is.
    When i uploaded your code, i had this error.
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    error: failed reading byte
    warning: espcomm_send_command: cant receive slip payload data
    warning: espcomm_sync failed
    error: espcomm_open failed
    error: espcomm_upload_mem failed
    error: espcomm_upload_mem failed
    I used PL2302 to upload code for ESP8266v1.
    And my connections:
    ESP8266 USB UART
    TX RX
    RX TX
    Vcc 3.3V
    GND GND
    CH_PD 3.3V
    Thank you.

    Liked by 1 person

  26. Pingback: Using NodeMCU ESP8266 + RFID + PHP for doing something – weltversteher.de

  27. tsuhan says:

    Hi, just a question, maybe not relate with this post.
    is it possible my UNO connect to Firebase via NodeMCU. My UNO act as a main controller, and i wan my nodemcu act as just a gateway for UNO to connect to Wifi. And i wan the code is on the UNO instead of on nodemcu.
    Hopefully, will get some idea from you. Thanks you. =D

    Liked by 1 person

    • antepher says:

      Hi!

      I don’t know which protocols Firebase supports, but I’m assuming it is one that can be used on the ESP (such as HTTP).

      If so, you should be able to what you mentioned.

      You need to send the data you want from the uno to the ESP and then the ESP should build the HTTP request from that data and send it to firebase.

      The easiest way to make the uno and the NodeMCU talk is by serial communication.

      Note however that the ESP works with 3.3 V and Uno with 5 V (at least the older versions) so you will need to perform level conversion.

      Nonetheless you will need to program the NodeMCU to do it in the most efficient way.

      The only alternative for not programming the NodeMCU is using the ESP AT commands, but I would recommend against it since they are not very reliable or flexible (at least they weren’t a couple of time ago).

      Bottom line, my recommendation is that you take a while to learn how to program the ESP8266 and think about using only it.

      The ESP8266 if far more powerful than the Uno and if you develop a program to it you will not need to worry about the level conversion and converting from serial to HTTP.

      Hope it helps,
      Nuno Santos

      Like

  28. ramachandran says:

    hi send library details

    Like

  29. Jeroen Elferink says:

    Hey,
    I’m using the esp8266 to get data from an API that the dutch railways provide, they return some xml data, however I can connect to the api. I am using the ESP8266HTTPClient library but the http.connected() is always 0. How do I get it to be a usable number? And how can I process XML data with the ESP8266?
    Thanks in advance for your help!

    Liked by 1 person

    • antepher says:

      Hi!

      In the code from this tutorial I’m not making any call to the http connected method. Are you using a modified version?

      Nonetheless, that method should return true if the tcp connection is ok and false otherwise, so you may be experiencing some problems with the connection.

      Are you able to use the same ESP8266 code to reach other websites with success? And are you able to reach the railway api and get the response with other tool, such as Postman or cURL?

      Regarding the XML processing, I’m not aware of any good parser for the ESP8266 or the Arduino. Only know for JSON format.

      Best regards,
      Nuno Santos

      Like

  30. Jeroen Elferink says:

    Hey,
    I’m using the esp8266 to get data from an API that the dutch railways provide, they return some xml data, however I can connect to the api. I am using the ESP8266HTTPClient library but the http.connected() is always 0. How do I get it to be a usable number? And how can I process XML data with the ESP8266?
    Thanks in advance for your help!

    Like

  31. rahul says:

    I want to Controll My Relay is this possible from above code??

    Liked by 1 person

    • antepher says:

      Hi!

      Well, you can do some sort of polling mechanism where you use an HTTP request to ask the server if you should connect your relay or not.

      Nonetheless, that would not be the most efficient approach.

      A better alternative would be setting a server on your ESP, which would in that case receive requests from a client to control the relay.

      You can check here how to get started:
      https://techtutorialsx.com/2016/10/03/esp8266-setting-a-simple-http-webserver/

      Note however that you will only be able to reach the server from inside your local network, unless you portforward your router, which may be a little bit more complicated if you are not used to such procedure, and also expose your network to some dangers.

      If you need to send commands to your relay from outside the local network, then a safer way may be opening a socket connection to the server and receive the commands from that interface.

      But it’s a matter of deciding which plays best for the requirements of your application.

      Best regards,
      Nuno Santos

      Like

  32. vakiyt says:

    Code works thanks,but how i can activate pin if i receive “1” from some URL,how i can transfer that 1 to Arduino and activate pin?

    Liked by 1 person

    • antepher says:

      Hi!

      What do you mean by receiving the 1 in the URL? Is your ESP8266 working as a webserver (thus receiving HTTP requests) or are you making a request from your ESP8266 to a URL?

      If you are making a request, then you would receive that 1 in the answer of the request.

      In that case, you would need to parse the result to an integer and check if it has the value 1.

      If it does, simply activate the pin by calling the digital write function:
      https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/

      As indicated in that page, don’t forget to initialize the pin as Output before using it.

      Hope this helps.

      Best regards,
      Nuno Santos

      Like

  33. Hakan Tutkun says:

    Hi , code works fine. It is really simple and useful.

    Thanks for this great tutorial 🙂

    Liked by 1 person

  34. vamsi krishna says:

    hi antephar
    i need a help
    i am trying to form a cluster with nodemcu modules, where one nodemcu act as server and other nodemcus act as clients. my problem here is i want to request the data from the particular client by IP address from the server. Is it possible by the http.get() method.
    thank u

    Liked by 1 person

    • antepher says:

      Hi!

      I’m not sure if I understood the architecture correctly, but you will have one NodeMCU as server and the remaining as clients, right?

      If so, I think it should be the clients asking data to the server and not the other way around. At least for a typical approach 🙂

      Why do you need to have the server contacting the clients? In that case, maybe you should have the other NodeMCUs working as servers and the one that is asking working as client.

      Does this make sense for your architecture?

      Best regards,
      Nuno Santos

      Like

  35. gourish says:

    hi
    i am getting connection refused error when the http command is executed after some seconds.

    Liked by 1 person

    • antepher says:

      Hi!

      Which endpoint are you trying to reach? Can you also reach it from a web browser?

      Also, is it HTTP or HTTPS? This example doesn’t work for HTTPs.

      Best regards,
      Nuno Santos

      Like

  36. Daniel says:

    Could you help me?
    I’m working with two Nodemcu. There is a server (access point) and a client. I got how to send requests from client to server, but I don’t know how to get those requests using the server.

    Liked by 1 person

    • antepher says:

      Hi!

      What do you mean by getting them in the server? Which library are you using?

      The typical implementations of webservers on the esp8266 / esp32 use the concept of routes.

      Whenever you receive a request on a route, it executes a route handling function, so is there that you handle the request.

      Then on those routes there are functions to access the parameters of the request.

      The parameters available will pretty much depend on the type of request (POST, GET, etc..), what you send on the query string etc..

      But let me know a little bit more about what you are doing so I can try to help 🙂

      Best regards,
      Nuno Santos

      Liked by 1 person

  37. Shariq Azim says:

    Hi this might sound silly, but im always getting http code 302 for a particular rest API(accessible without logging in ). Also, postman app gives me response as 200 along with payload . http://jsonplaceholder.typicode.com/users/1 gives perfect response with nodeMCU.
    thus im not able to parse contents,

    Please help.!!!
    im just passing some headers along with the get request
    snippet:
    http.begin(“my rest url”); //Specify request destination
    int httpCode = http.GET(); //Send the request
    Serial.println(httpCode); // returns302
    if (httpCode > 0) { //Check the returning code

    String payload = http.getString(); //Get the request response payload
    Serial.println(payload); //Print the response payload

    }

    http.end();

    BTW, it returns -1 when any any other url is used ;(

    Liked by 1 person

    • Shariq Azim says:

      a bit modification:

      snippet:
      http.begin(“my rest url”); //Specify request destination does not have www including http
      http.addHeader(“Accept”, “application/json”);
      http.addHeader(“Content-Typez”, “application/json”);
      http.addHeader(“location”, “same URL including https);
      int httpCode = http.GET(); //Send the request
      Serial.println(httpCode); // returns302
      if (httpCode > 0) { //Check the returning code

      String payload = http.getString(); //Get the request response payload
      Serial.println(payload); //Print the response payload

      }

      http.end();

      Liked by 1 person

      • antepher says:

        Don’t forget the http://
        You should use http://yourURL

        Note also that content-type header as a typo (a Z at the end that should not be there)

        Does your endpoint work if you don’t specify any headers?

        Best regards,
        Nuno Santos

        Like

    • antepher says:

      Hi! That is very weird.

      When using postman, did you also send the same headers?

      Is your REST URL HTTP or HTTPS? Also, does it end with a / ? If so, are you including it? I’ve seen people having some problems with it because of not including the ending /.

      Other than that it is very weird since 302 is redirection code.

      Is the REST API public or hosted by you?

      Best regards,
      Nuno Santos

      Like

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