How to fix error during connect: Get http://docker:2375/v1.40/info: dial tcp: connect: connection refused in Docker

sudo systemctl status docker

Get-Service *docker*

# Linux
sudo systemctl start docker

# Windows/macOS
# Open Docker Desktop application

echo $DOCKER_HOST

unset DOCKER_HOST
docker version

# .gitlab-ci.yml
image: docker:latest

services:
  - docker:dind

variables:
  # CORRECT: Use 'docker' hostname for the dind service
  DOCKER_HOST: tcp://docker:2375

  # For TLS-enabled Docker 19.03+:
  # DOCKER_HOST: tcp://docker:2376
  # DOCKER_TLS_CERTDIR: "/certs"
  # DOCKER_CERT_PATH: "/certs/client"
  # DOCKER_TLS_VERIFY: 1

build:
  script:
    - docker version
    - docker build -t myimage .

jobs:
  build:
    runs-on: ubuntu-latest
    services:
      dind:
        image: docker:dind
        options: --privileged
        ports:
          - 2375:2375
        env:
          DOCKER_TLS_CERTDIR: ""

    steps:
      - uses: actions/checkout@v4

      - name: Wait for Docker daemon
        run: |
          timeout 30 sh -c 'until docker info; do sleep 1; done'
        env:
          DOCKER_HOST: tcp://localhost:2375

      - name: Build image
        run: docker build -t myimage .
        env:
          DOCKER_HOST: tcp://localhost:2375

#!/bin/bash
# wait-for-docker.sh

echo "Waiting for Docker daemon..."
TIMEOUT=30
ELAPSED=0

while ! docker info >/dev/null 2>&1; do
  if [ $ELAPSED -ge $TIMEOUT ]; then
    echo "Timeout waiting for Docker daemon"
    exit 1
  fi
  echo "Docker not ready, waiting..."
  sleep 2
  ELAPSED=$((ELAPSED + 2))
done

echo "Docker daemon is ready!"
docker version

timeout 30 sh -c 'until docker info >/dev/null 2>&1; do sleep 1; done'

curl http://localhost:2375/version
# or
docker -H tcp://localhost:2375 version

sudo mkdir -p /etc/systemd/system/docker.service.d
sudo tee /etc/systemd/system/docker.service.d/override.conf << EOF
[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// -H tcp://127.0.0.1:2375
EOF

sudo systemctl daemon-reload
sudo systemctl restart docker

{
  "hosts": ["unix:///var/run/docker.sock", "tcp://127.0.0.1:2375"]
}

sudo systemctl restart docker

ss -tlnp | grep 2375
curl http://127.0.0.1:2375/version

# Check current rules
sudo ufw status

# Allow port 2375 (only if needed for remote access)
sudo ufw allow 2375/tcp

# Check if port is allowed
sudo firewall-cmd --list-ports

# Allow port 2375
sudo firewall-cmd --permanent --add-port=2375/tcp
sudo firewall-cmd --reload

# Check if port is blocked
netsh advfirewall firewall show rule name=all | findstr "2375"

# Allow port (PowerShell as Administrator)
New-NetFirewallRule -DisplayName "Docker TCP" -Direction Inbound -LocalPort 2375 -Protocol TCP -Action Allow

# Using netcat
nc -zv docker 2375
nc -zv localhost 2375

# Using curl
curl -v http://docker:2375/version
curl -v http://localhost:2375/version

# Using telnet
telnet docker 2375

# Linux
ss -tlnp | grep 2375
netstat -tlnp | grep 2375

# Windows
netstat -ano | findstr 2375

# Check if 'docker' hostname resolves
getent hosts docker
nslookup docker

# In Kubernetes, check service discovery
kubectl get svc
kubectl get endpoints