Tailcat, an open‑source tool built on Tailscale components, allows users to create netcat‑style connections over Tailscale’s encrypted data plane without using Tailscale’s control plane. Tailscale’s data plane encrypts traffic between devices using WireGuard and routes it through DERP relays when direct connection fails. Tailcat leverages these capabilities by handling connection setup outside of Tailscale’s control plane, enabling peer‑to‑peer tunnels with minimal configuration. The command‑line interface runs a server that prints a connection token and waits for a client to connect using that token. All traffic is end‑to‑end encrypted with WireGuard; the initial handshake occurs through a DERP relay and then upgrades to a direct peer‑to‑peer UDP connection when NAT traversal succeeds. The tool supports port forwarding, exposure of local TCP ports, an SSH server that can operate without authentication, a SOCKS5 proxy, and a ping utility that reports whether traffic travels via DERP or a direct path. Key management allows ephemeral keys that generate a fresh token for each run or saved keys that provide a persistent address; tokens can also be published as DNS TXT records for name‑based access. Installation is available via Go install or Nix commands, and a web demo compiled to WebAssembly lets browsers send and receive data through DERP relays. The project is open source, offers no formal support or stability guarantees, and relies on rate‑limited DERP relays that may be revoked at any time.