Docker Expose Port 800

Expose Port 800 in Docker

docker run -p 800:800 your-image-name
		

This command maps container port 800 to the same port on the host machine.

Dockerfile Example

FROM node:18-alpine
WORKDIR /app
COPY . .
EXPOSE 800
CMD ["npm", "start"]
		

The EXPOSE instruction documents that the container listens on port 800.

EXPOSE vs Publish (-p)

• EXPOSE 800 documents the port inside the container.
• -p 800:800 makes the port accessible from the host.
• Exposed ports are not reachable unless published.

Docker Expose Port 800 Not Working

If Docker expose port 800 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 800 Already in Use

The error “port 800 already in use” means another process is already bound to that port on your host system.

# Find process using port 800
lsof -i :800

# OR use a different host port
docker run -p 8080:800 your-image-name
		

• Ensure your app is listening on port 800 inside the container
• Verify the port is published using -p
• Check firewall or network rules
• Avoid conflicts with existing services

Related Docker Expose Port Guides