Accessing Ports Inside Docker AI Sandboxes (Workaround)

Docker recently introduced Docker Sandboxes (currently Experimental), a fantastic feature that provides isolated microVM environments for AI coding agents like Claude Code, Copilot, and others. However, as of early 2026, there is one missing feature that many developers are waiting for: native port forwarding . If your AI agent spins up a local web server (e.g., a React app on port 3000 or a Python API on 8000) inside the sandbox, you cannot access it from your host machine's browser using the traditional docker run -p approach. Official support is on the roadmap, but what if you need to preview it right now ? Here is a quick and elegant workaround using socat and netcat to tunnel TCP traffic through the standard I/O of docker sandbox exec . The Solution: Standard I/O Tunneling We can map a port on our host machine to a port inside the sandbox by piping a TCP connection through docker sandbox exec -i . To handle multiple simultaneous connections (like loading HTML, CSS, and JS files fr