Docker Expose Port 540

Expose Port 540 in Docker

docker run -p 540:540 your-image-name
		

This command maps container port 540 to the same port on the host machine.

Dockerfile Example

FROM node:18-alpine
WORKDIR /app
COPY . .
EXPOSE 540
CMD ["npm", "start"]
		

The EXPOSE instruction documents that the container listens on port 540.

EXPOSE vs Publish (-p)

• EXPOSE 540 documents the port inside the container.
• -p 540:540 makes the port accessible from the host.
• Exposed ports are not reachable unless published.

Docker Expose Port 540 Not Working

If Docker expose port 540 is not working, it is usually due to incorrect port publishing, an application not listening on the expected port, or a port conflict on the host machine.

Port 540 Already in Use

The error “port 540 already in use” means another process is already bound to that port on your host system.

# Find process using port 540
lsof -i :540

# OR use a different host port
docker run -p 8080:540 your-image-name
		

• Ensure your app is listening on port 540 inside the container
• Verify the port is published using -p
• Check firewall or network rules
• Avoid conflicts with existing services

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