从一个 docker 容器连接到另一个 [相同网络] 时连接被拒绝

Question

Having a hard time debugging this. I have one container starting an MQTT server and another Python container trying to connect.

Using docker-compose to orchestrate and have set up a network and connected both containers to it.

Currently I can connect to the MQTT server independently with docker run and with docker-compose, but the Python containe for some reason cannot connect.

I'm thinking it may be a firewall issue?

In the main.py I'm printing the MQTT_HOST and MQTT_PORT and I can actually connect to those using a local Mosquitto client.

docker-compose.yml

version: "3.3"
services:
  webserver:
    build: ./webservice/server
    ports:
      - 3001:3001
      - 3002:3002
    networks:
      - project-network
    command: npm run start
  inferemce:
    build: ./inference
    ports:
      - 3003:3003
    networks:
      - project-network
    depends_on:
      - webserver
    restart: on-failure
    command: ["./wait-for-it.sh", "webserver:3001", "--", "python", "main.py"]

networks:
  project-network:
    driver: bridge

main.py

import socket
import paho.mqtt.client as mqtt

HOSTNAME = socket.gethostname()
IPADDRESS = socket.gethostbyname('localhost')
MQTT_HOST = IPADDRESS
MQTT_PORT = 3001
MQTT_KEEPALIVE_INTERVAL = 60

def connect_mqtt():
    print('host', MQTT_HOST)
    print('port', MQTT_PORT)
    client = mqtt.Client()
    client.connect(MQTT_HOST, MQTT_PORT, MQTT_KEEPALIVE_INTERVAL)
    return client

def main():
    client = connect_mqtt()



if __name__ == '__main__':
    main()

Answer 1

You are trying to connect to localhost which is going to be the container the python app is running in, not webserver .

Change the python to try to look up the address of webserver rather than localhost

import socket
import paho.mqtt.client as mqtt

HOSTNAME = socket.gethostname()
IPADDRESS = socket.gethostbyname('webserver')
MQTT_HOST = IPADDRESS
MQTT_PORT = 3001
MQTT_KEEPALIVE_INTERVAL = 60
...