How to establish Docker Connection to Localhost Development Server

I'm trying to connect a Mage.ai pipeline to an endpoint of my development server (a microservice of my app). However, I barely have any knowledge on the topic and it's getting rough.

My app uses Vue and Flask and these are the steps I've followed until now:

1. I checked that the endpoint is valid.

   curl -X POST http://localhost:4999/user/login -H "Content-Type: application/json" -d '{"username": "USERNAME", "password": "PASSWORD"}'

   Returns me an OK and a valid token.

2. Setted the app to run on 0.0.0.0, on both the microservice and the login endpoint. These are the lines of my login endpoint, for example:

   if __name__ == '__main__':
       app.run(
           host='0.0.0.0',  
           # host='127.0.0.1',
           port='4999',
           debug = True
       )
   

     WARNING: This is a development server. Do not use it in a production deployment.
      Use a production WSGI server instead.
    * Debug mode: on
    * Running on http://0.0.0.0:4999/ (Press CTRL+C to quit)
    * Restarting with stat
   

   This is the Vue message:

     App running at:
     - Local:   http://localhost:9528/ 
     - Network: http://172.22.15.213:9528/
   

3. Did a ping to establish a connection with that network address:

   root@fcf10b9466d3:/home/src/pipelines/actualizarfirmas_test# ping 172.22.15.213
   
   PING 172.22.15.213 (172.22.15.213) 56(84) bytes of data.
   
   ^C
   
   --- 172.22.15.213 ping statistics ---
   
   52 packets transmitted, 0 received, 100% packet loss, time 52210ms
   

And that's it because I do not know what else to do.

This is my microservice important flask lines:

@app.route('/receive_results', methods=['POST'])
def receive_results():
    data = request.json
    print("Received results:", data)

    status = data.get("status_received")
    message = data.get("message_received")

    return jsonify({
        "status_received": status,
        "message_received": message,
        "details": "Conexión exitosa con la API."
    })

if __name__ == '__main__':

    app.run(
        host='0.0.0.0',  
        # host='127.0.0.1',  
        port='5009',
        # debug = True,
        # threaded=False
    )

This is the way I intended to connect with my microservice (I just wanted to send back a response of the status of the pipeline, fail, success and why):

import requests

def enviar_mensaje_amic(custom_args, res, msg, token): 
    custom_args['status_received'] = res
    custom_args['message_received'] = msg 
    print(res)
    print(token)
    print(msg)
    try:
        result = {
            "status_received": custom_args['status_received'],
            "message_received": custom_args['message_received'],
            "execution_details": "Custom results."
        }
        headers = {
            "Authorization": f"Bearer {token}",
            "Content-Type": "application/json"
        }
        response = requests.post("http://172.22.15.213:5009/receive_results", json=result, headers=headers)
        print(response.status_code)
        print(response.json()) 
        print("Datos recibidos:", response.status_code)
    except Exception as e:
        print(f"Error al enviar datos: {e}")
    return 

def amic_login(custom_args, config_data):
    base_url = "http://172.22.15.213:4999"
    login_endpoint = f"{base_url}/user/login"

    userdata = custom_args.get('userdata', [])
    user = userdata[0]
    pwd = userdata[1]

    payload = {
        "username": user,
        "password": pwd
    }
    try:
        response = requests.post(login_endpoint, json=payload)
        response_data = response.json()
        if response.status_code != 200 or "token" not in response_data:
            raise Exception(f"Autentificación fallida: {response_data.get('message', 'Incógnita...')}")
            # MIRAR CUÁL ES LA ESTRUCTURA DEL JSON QUE SE DEVOLVERÍA (PRODUCIDO POR AMIC, ESTO ES UNA BASE GUÍA!)
        return response_data['token']
    except Exception as e:
        raise Exception(f"Error inesperado durante la autentificación: {str(e)}")