TCPSER turns a PC serial port into an emulated Hayes compatible modem that
uses TCP/IP for incoming and outgoing connections.  It can be used to allow
older applications and systems designed for modem use to operate on the
Internet.  TCPSER supports all standard Hayes commands, and understands
extended and vendor proprietary commands (though it does not implement
many of them).  TCPSER can be used for both inbound and outbound connections.

WWW: http://www.jbrain.com/pub/linux/serial/