Sending GET request from arduino using esp8266 wifi module to a nodejs server

I'm trying to send a GET request to an nodejs server (using express) from arduino mega using the wifi module esp8266 with the AT-Commands.

It seems the server doesn't receive nothing even if in the arduino serial monitor I can read "SEND OK" when the server is running.

The same command sent from arduino to an flask server works. With the Chrome browser the I have no problems, both nodejs server and flask receive the request.

I have spent a lot of days finding a solution for this problem, I don't understand where I am wrong.

Arduino code for sending request:

void sendGetRequest(String ip, int port, String buttonId) {
String command = "AT+CIPSTART=0,\"TCP\",";
command += "\"";
command += ip;
command += "\",";
command += port;
command += "\r\n";

sendData(command, 1000, DEBUG);
sendData("AT+CIPSEND=0,15\r\n", 1000, DEBUG);

String request = "GET /b1";
sendData(request, 1000, DEBUG);
sendData(" \r\n", 1000, DEBUG);
sendData(" \r\n", 1000, DEBUG);
sendData(" \r\n", 1000, DEBUG);

//sendData("AT+CIPCLOSE=4\r\n", 1000, DEBUG);
}

String sendData(String command, const int timeout, boolean debug) {
  String response = "";

  esp8266.print(command); // send the read character to the esp8266

  long int time = millis();

  while ((time+timeout) > millis()) {
    while (esp8266.available()) {

      // the esp has data so display its output to the serial window 
      char c = esp8266.read(); // read the next character.
      response+=c;
    } 
  }

  if (debug) {
    Serial.print(response);
  }

  return response;
}

NodeJs express endpoint:

var http = require('http');

//Server port
var port = 6882;

//Web server
var app = express();
var server = http.createServer(app);
server.listen(port, "0.0.0.0");

app.get('/b1', function (req, res) {
    console.log("Button pressed!" ); 
    res.send("Hello");
});

Flask simple server that works:

from flask import Flask
app = Flask(__name__)

@app.route("/b1", methods=["GET"])
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5000)

Thanks for your help, and sorry for my bad english.

via Cosimo Lovascio