Arduino gets response from server problem

Question

I'm using an ESP8266 connected to an Arduino Uno via SoftwareSerial to make a post request to an API. The ESP8266 is able to connect to a WIFI connection. When I try to send some data (temperatures values captured by the module DHT22) to the server I always get a access denied. It always happens when the command "esp.println(tcpstart)" is executed and I receive the response "--> Cannot initiate TCP connection" in the Serial Monitor thanks to the prints I added. "tcpstart" is the AT command "AT+CIPSTART". The Arduino Uno is flashed with the firmware: ai-thinker-0.9.5.2-115200.bin. This is my code:

#include <SoftwareSerial.h>
#include <DHT.h>;
#define RX_PIN 2
#define TX_PIN 3
#define DHTTYPE DHT22
#define DHTPIN  7

SoftwareSerial esp(RX_PIN, TX_PIN); // Rx,  Tx
DHT dht(DHTPIN, DHTTYPE);
float temp;
String ssid = "XXXXX";
String pass = "YYYYY";
//Complete API URL to do the post: https://api.test.com:bbbb/zzz/zzzz/v2/z?zzzzzzz
String server = "https://api.test.com";
String ip = "aa.aaa.aa.aa";
int port = bbbb;
String uri = "/zzz/zzzz/v2/z?zzzzzzz";
bool connection;
String data;
String* response;

void setup(){
  Serial.begin(9600);
  esp.begin(115200);
  esp.setTimeout(5000);
  dht.begin();
}

void loop(){
  reset();
  readSensors();
  while(connection == false)
    connectWifi();
  connection = false;
  httppost();
}

void readSensors(){
  temp = dht.readTemperature();
  data = String(temp);
}

void reset(){
  esp.println("AT+RST");
  delay(300);
  esp.println("AT+CWMODE=1");
  delay(300);
  esp.println("AT+RST");
  delay(300);
  esp.println("AT+CIPMUX=0");
  delay(300);
}

void connectWifi(){
  String cmd = "AT+CWJAP=\"" + ssid + "\",\"" + pass + "\"";
  delay(300);
  esp.println(cmd);
  if(esp.find("OK")){
    Serial.println("Wifi Connected");
    connection = true;
  }else{
    Serial.println("--> Wifi not Connected");
    connection = false;
  }
}

void httppost(){
  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;
  String tcpStart = "AT+CIPSTART=\"TCP\",\"" + ip + "\"," + port;
  String sendCmd = "AT+CIPSEND=" + postRequest.length();
  esp.println(tcpStart); //start TCP connection
  delay(300);
  if(esp.find("OK")){
    Serial.println("TCP connection OK");
    esp.println(sendCmd); //send the data over TCP connection
    delay(300);
    if(esp.find(">")){
      Serial.println("Sending packet");
      esp.println(postRequest);
      delay(300);
      if(esp.find("SEND OK")){
        Serial.println("Packet sent");
        while(esp.available()){ //number of bytes/char available for reading
          char tmpResp = esp.read(); //read one char at the time
          Serial.print(tmpResp);
          if (tmpResp == '\0') continue; //terminate the while when end of the data
        }
        esp.println("AT+CIPCLOSE"); //close TCP connection
      }else{
        Serial.println("--> An error occured while sending packet");
      }
    }else{
        Serial.println("--> ESP8266 is not listening for incoming data");
    }
  }else{
    Serial.println("--> Cannot initiate TCP connection");
  }
}

Do you have an idea of the problem it might be?

Arun P Arun P · Accepted Answer · 2019-08-28T12:26:58

Try this code.

#include <SoftwareSerial.h>

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

SoftwareSerial ESP8266 (rxPin, txPin);

unsigned long lastTimeMillis = 0;

void setup() {
  Serial.begin(9600);   
  ESP8266.begin(9600);
  delay(2000);
}

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\",\"192.168.1.19\",80");
    delay(1000);
    printResponse();

    String cmd = "GET /test.html 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());
  }

}

Arduino gets response from server problem

1 Answers