How to connect the docker fast api with mqtt broker?

Without docker, I could connect my fastapi app with mqtt broker. However with docker, I cannot connect my fastapi app with the docker mqtt broker. I get the error –

{"log":"    ', '.join(str(exc) for exc in exceptions)))n","stream":"stderr","time":"2022-02-21T04:42:21.137558005Z"}
{"log":"OSError: Multiple exceptions: [Errno 111] Connect call failed ('127.0.0.1', 1883), [Errno 99] Cannot assign requested addressn","stream":"stderr","time":"2022-02-21T04:42:21.137562299Z"}
{"log":"n","stream":"stderr","time":"2022-02-21T04:42:21.137566492Z"}
{"log":"ERROR:    Application startup failed. Exiting.n","stream":"stderr","time":"2022-02-21T04:42:21.137570669Z"}

Here is my main.app

from fastapi import FastAPI
from fastapi_mqtt import FastMQTT, MQTTConfig
from pydantic import BaseModel
from ipaddress import IPv4Address
import jsonpickle

app = FastAPI()


class Nmap(BaseModel):
    host: IPv4Address
    portRange: str

    class Config:
        schema_extra = {
            "example" : {
                "host": "10.0.2.15",
                 "portRange": "22-80",
                 "description": "Scan the port from 22 to 80 of the ip address 10.0.2.15"
            }
        }



mqtt_config = MQTTConfig()

mqtt = FastMQTT(config=mqtt_config)

mqtt.init_app(app)

@mqtt.on_connect()
def connect(client, flags, rc, properties):
    mqtt.client.subscribe("/mqtt/toModel/#") # subscribing mqtt topic wildcard- multi-level
    print("connected: ", client, flags, rc, properties)

@mqtt.on_message()
async def message(client, topic, payload, qos, properties):
    print("received message: ", topic, jsonpickle.decode(payload.decode()), qos, properties)
    return 0 


@mqtt.on_disconnect()
def disconnect(client, packet, exc=None):
    print("Disconnected")

@mqtt.on_subscribe()
def subscribe(client, mid, qos, properties):
    print("subscribed", client, mid, qos, properties)

@app.get("/")
async def func():
    mqtt.client.publish("/mqtt", "Hello from fastApi") 
    return {"result": True, "message": "Published"}

@app.post("/scan/{host}")
async def scan_host_port(nmap_details : Nmap):
    results = {"got_val" : nmap_details}
    print(type(nmap_details))
    mqtt.client.publish("/mqtt/fromModel/nmap", jsonpickle.encode(nmap_details)) 
    return results

Here is my app docker file –

FROM python:3.7

WORKDIR /code 


COPY ./requirements.txt /code/requirements.txt


RUN pip install -r /code/requirements.txt


COPY ./app /code/app

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]

For MQTT, I am using –

docker-compose.yml

version: "3"
services:
 mqtt:
      image: toke/mosquitto
      network_mode: bridge
      container_name: mqtt
      expose:
        - 1883
      ports:
        - 1883:1883
      restart: unless-stopped

I am sure it is something with my docker but I don’t know how to deploy it.My understanding is that docker is designed to run a single process. So one process for broker, another docker to simply run my fast api and another docker for nginx