This is my appsettings.Production.json file, I am using a different port number than the default.

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "DefaultConnection": "Server=docker-demo-sqlserver,1432;Database=DockerComposeDemo;User=sa;Password={0};TrustServerCertificate=True"
  }
}

And this is my docker-compose file

version: '3.8'

services:
  docker-demo-web-api:
    container_name: docker-demo-web-api-container
    build:
      context: .
      dockerfile: DockerDemoWebApi/Dockerfile
    environment:
      - MSSQL_SA_PASSWORD=Password1*
    ports:
      - "5000:8080"
    depends_on:
      - docker-demo-sqlserver    
  docker-demo-sqlserver:
    container_name: docker-demo-sqlserver-container
    image: mcr.microsoft.com/mssql/server:2022-latest
    environment:
      - ACCEPT_EULA=Y
      - MSSQL_SA_PASSWORD=Password1*
    ports:
      - "1432:1432"

Although I use the same port number in the docker-compose file The app cannot find the docker-demo-sql server service.

When I change the port number to 1433 in the connection string, it works well even I don’t change the docker-compose port number(1432:1432).

I don’t understand, it seems the app or SQL service doesn’t care the port number in the docker-compose file. Only When I change the port number 1433 to 1432 in the connection string it gives errors.