Because no service is running on that port, or a firewall is blocking the connection. See Part 4.

: Install the CLI utility and run ngrok http 11501 to map your local port into a public, secure HTTPS endpoint.

A port functions as a digital communication endpoint. Standard web traffic relies on default ports, such as port 80 for HTTP and port 443 for HTTPS. However, developer environments use alternative or private ports ranging from 1024 to 65535 to prevent system-level conflicts. Port 11501 belongs to this unassigned registration block, making it ideal for specialized developer configurations, internal APIs, node processes, or enterprise software instances. Technical Comparison: Standard vs. Custom Developer Ports

When working with , you may encounter several errors. Here’s how to fix the most frequent ones.

[ User Web Browser ] │ Requests URL: http://localhost:11501 │ ▼ [ OS Loopback Interface ] ───► (Stays inside the PC) │ ▼ [ Target Application ] (Listening on Port 11501) Common applications running on this port include:

Jupyter often runs on random ports (e.g., 8888, 8890). A less common configuration or multi-user setup might land on 11501.

This shows the process name and PID.