A simple http POST example

[xseignard]

Hello,

I just recieved the cactus micro board and it seems pretty promising!

But I'm trying to do a HTTP POST from the board to a distant server, but I can't find any documentation/examples about it.

I managed to connect to wifi following the temperature logger example, but cannot perform a HTTP POST.

Any examples available?

Regards,

Xavier

[volca]

I will make an example these days.

[xseignard]

Thanks! This is more than welcomed!

Regards,

Xavier

[xseignard]

So i tried myself and went there https://gist.github.com/xseignard/a650f241b434eb1b296a

I can connect to the wifi, but I cannot initiate the TCP connection, any idea?

Regards

[volca]

I'm writing a library to handle http request. I will check your code today.

[xseignard]

I checked your comments and tried your tips, but i still cannot POST. The TCP connection seems to fail. I use a simple node.js/express.js server to receive the posts:

var express = require('express'),
    bodyParser = require('body-parser'),
    app = express();

app.use(bodyParser.urlencoded({ extended: false }));

app.get('/', function (req, res) {
    res.send('Hello World!');
});

app.post('/event', function(req, res) {
    console.log(req.body);
    res.status(200).send();
});

var server = app.listen(3000, function () {
    var host = server.address().address;
    var port = server.address().port;
    console.log('Example app listening at http://%s:%s', host, port);
});

And I can reach this server with the following:

 curl -X POST -d "data=42" http://192.168.1.24:3000/event

[xseignard]

With that tiny script I can send AT commands from arduino monitor

#include <SoftwareSerial.h>

// ESP8266 rx, tx
SoftwareSerial esp8266(11, 12);

void setup() {
  delay(5000);
  Serial.begin(9600);
  esp8266.begin(9600);
  // enable wifi
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  delay(1000);
}

void loop()
{
  if (Serial.available() > 0) {
    char ch = Serial.read();
    esp8266.print(ch);
  }
  while (esp8266.available() > 0) {
    char ch = esp8266.read();
    Serial.print(ch);
  }
}

So I tried to send a AT+CIPSTART="TCP","192.168.1.24",3000 and here was the result:

CONNECT

OK

So it seems it should work for my initial sketch too since i'm trying to find "OK" in the buffer, I also tried to find "CONNECT" with no more success.

I really don't get it, and if i cannot initiate a TCP connection, the cactus micro is just a plain old arduino micro...

Here is the result of a AT+GMR

00200.9.5(b1)
compiled @ Dec 25 2014 21:40:28
AI-THIN

I'm really stuck here...

[volca]

I'm testing HTTP post code these days but no luck. The problem is it always lose the "\r\n\r\n" in the POST content.

But for HTTP get, it works well.

I wrote a blog How to change the serial port for Cactus Micro. Use hardware serial port is much stable than software serial.

[xseignard]

Any idea why I cannot initiate the TCP connection from my arduino code, but I can when I type the AT command directly?

[volca]

I think the module haven't got IP when you tried to create TCP connection. Please add a delay(5000) after joined AP.

[xseignard]

Thanks, i can now initiate a TCP connection

Here is my code for now:

#include <SoftwareSerial.h>

// ESP8266 rx, tx
SoftwareSerial esp8266(11, 12);

void setup() {
    //connection to ESP8266
    esp8266.begin(9600);
    esp8266.setTimeout(2000);
    //serial debug
    Serial.begin(9600);

    // enable wifi
    pinMode(13, OUTPUT);
    digitalWrite(13, HIGH);
    delay(1000);

    if (check()) {
        resetESP8266();

        if (connectWifi("crepeFlambee", "!rfvcde1984")) {
            delay(5000);
            String response="";
            boolean ok = httpPOST("test=42", "192.168.1.24", 3000, "/event", &response);
            if (ok) {
                Serial.println(response);
            }
            else {
                Serial.println("Something went wrong while posting data");
            }
        }
    }
}

void loop() {
}

boolean check() {
    esp8266.println("AT");
    Serial.println("checking..");
    boolean ok = false;
    if (esp8266.find("OK")) {
        Serial.println("ESP8266 available");
        ok = true;
    }
    return ok;
}

void resetESP8266() {
    // reset ESP8266
    esp8266.println("AT+RST");
    delay(500);
    // set station mode
    esp8266.println("AT+CWMODE=1");
    delay(200);
    // set single connection mode
    esp8266.println("AT+CIPMUX=0");
    delay(200);
}

boolean connectWifi(String ssid, String password) {
    String cmd = "AT+CWJAP=\"" + ssid + "\",\"" + password + "\"";
    esp8266.println(cmd);
    if(esp8266.find("OK")) {
        Serial.println("Connected!");
        return true;
    }
    else {
        Serial.println("Cannot connect to wifi");
        return false;
    }
}

boolean httpPOST(String data, String server, int port, String uri, String* response) {
    // initiate TCP connection
    String tcpStart = "AT+CIPSTART=\"TCP\",\"" + server + "\"," + port;
    Serial.println(tcpStart);
    // prepare the data to be posted
    String postRequest =
        "POST " + uri + " HTTP/1.1\r\n" +
        "Host: " + server + ":" + port + "\r\n" +
        "Accept: *" + "/" + "*\r\n" +
        "Content-Length: " + data.length() + "\r\n" +
        "Content-Type: application/x-www-form-urlencoded\r\n" +
        "\r\n" +
        data;

    // notify ESP8266 about the lenght of TCP packet
    String sendCmd = "AT+CIPSEND=" + postRequest.length();

    esp8266.println(tcpStart);
    if (esp8266.find("OK")) {
        Serial.println("TCP connection OK");
        esp8266.println(sendCmd);
        if (esp8266.find(">")) {
            Serial.println("Sending packet...");
            esp8266.println(postRequest);
            if (esp8266.find("SEND OK")) {
                Serial.println("Packet sent");
                while (esp8266.available()) {
                    String tmpResp = esp8266.readString();
                    response = &tmpResp;
                }
                // close the connection
                esp8266.println("AT+CIPCLOSE");
                return true;
            }
            else {
                Serial.println("An error occured while sending packet");
                return false;
            }
        }
        else {
            Serial.println("ESP8266 is not listening for incoming data");
            return false;
        }
    }
    else {
        Serial.println("Cannot initiate TCP connection");
        return false;
    }
}

Now I face the problem that I never find the > char telling the arduino it can start sending data. The road to POST with cactus micro is bumpy...

[volca]

I have made a http post sample today. I will re-organize the code tomorrow. The key function is F().

For example:

Serial1.println(F("AT+CIPSEND=100"));

It will save the string to flash and not ram.

[volca]

Hi,

I add a blog and a simple example for how to make http request. Please have a try.

[xseignard]

Hello, I don't see why you need to use the F macro?? Since the length of a tcp packet is variable it makes no sense to use the F macro

[xseignard]

I checked your blog post, the cactus micro is definitely not IOT ready... I'll give a try someday

[xseignard]

Any updates?

[volca]

Hi,

I have added a httpPost eample. Please have a look.

We are also testing the next revision Cactus Micro. The new version is make the hardware serial as default option.

I'd like to send you a free sample.

[xmoulin]

Hello, I just try the HTTP Post Example, with Arduino 1.6.5 IDE, and I got some errors:

cactus-httpPost:49: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:49: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:49: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost.ino: In function 'bool connectWifi()': cactus-httpPost:94: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:94: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost.ino: In function 'void setup()': cactus-httpPost:133: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:133: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:133: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost.ino: In function 'void httpPost(String)': cactus-httpPost:194: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:194: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:205: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:205: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' cactus-httpPost:205: error: converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)' converting to 'String' from initializer list would use explicit constructor 'String::String(int, unsigned char)'

pgmspace.h have change between version 1.0.6 and 1.5.6. some post about that: http://forum.arduino.cc/index.php?topic=273294.0

Regards, Xavier.

[volca]

Thank you for your reminder!

[hulvejen]

The httpPost eample. is displaying 404. Please update the link.

[volca]

Thank you. Link is fixed.

[loki077]

Thank you in advance ............for all this discussions ............:) The example links no more there if you can plzz try to post it back. I am also trying the POST command but its not working it seems same to me that ESP8266 is not taking /r/n command from all your discussion i get to understand that its an firm ware issue am i right? ?/????

[volca]

when did you buy the cactus micro? For rev2, the default firmware is ESPduino on ESP8266. Please try the rest.ino sketch.

[ArthurTimmermans]

You have to put some delays between your esp8266 calls, makes it more stable and you do not come further than:

if (esp8266.find(">")) {

because you have to make the command above a string.

String sendCmd = "AT+CIPSEND=" + String(postRequest.length());