Can't connect to SQL Server express from .net core app running on docker

Question

I have SQL Server 2016 Express, docker for Windows and IIS installed on my Windows 10 machine.

SQL Server Express is configured to listen on 1455 port. The Northwind

Answer 1

The problem was I didn't disable Windows Firewall correctly.

I turned off Windows Firewall, but only on Domain networks. Windows sees the DockerNAT adapter as a public network. So Windows firewall was blocking the connection to SQL Server.

I turned off Windows Firewall on public networks and I can connect now.

Answer 2

You can try to start the container using network mode as host. In that case the container can connect to applications running on the host machine using localhost as a DNS name.

version: '3'

services:
  connectsqlserver:
    image: connectsqlserver
    build:
      context: ./ConnectSqlServer
      dockerfile: Dockerfile
    network_mode: "host"