piko
An open-source alternative to Ngrok, designed to serve production
...It lets upstream services open outbound-only connections to Piko, then routes incoming traffic back through those established tunnels. This design is useful for services that are private, behind NAT, firewalled, or otherwise not publicly routable. Piko is built for production-oriented hosting rather than only short-lived development demos. It supports a server and agent model, with the agent running near the upstream service and forwarding traffic from named endpoints to local ports. The project also includes Kubernetes-oriented deployment guidance, clustering behavior, and a single binary that can run in both server and agent modes.