vmodemd is a telnet server designed to run old DOS BBS systems and door games. It listens for incoming TCP connections on a defined port, does a minimal telnet handshake if needed, and then starts to proxy all data to a PTY which is bound to a dosemu virtual serial port. vmodemd supports any number of virtual modems, can display customized banners if all modems are busy, can terminate a serial app when a telnet connection is unexpectedly dropped, and run custom scripts before passing control to dosemu, allowing you to pass relevant data like incoming IP address to the DOS app.