What are some alternatives?
When comparing MLDonkey and Portmap.io, you can also consider the following products
eMule - eMule is a free peer-to-peer file sharing application for Microsoft Windows.
ngrok - ngrok enables secure introspectable tunnels to localhost webhook development tool and debugging tool.
aMule - aMule - the all-platform P2P client!
Serveo - Use SSH to expose local servers over the internet and inspect and replay HTTP traffic.
Soulseek - Soulseek® is a unique ad-free, spyware free, and just plain free file sharing application.
Pagekite - Bring your localhost servers on-line.