Which product do I need - TNC or Piper?

TNC and Piper are similar products, they both convert RS232 data streams to Ethernet IP packets, but they are aimed at two different system applications -

Telnet Communicator.

TNC is designed to make allow a Telnet TCP connection directly to a remote V24 device. One or more units can be used to connect to remote V24 devices as shown below. TNC is configured using a web browser.

Piper.

Pipers are often used in pairs. In the example below, two units convert an RS232 data stream to Ethernet, send it across a network and then convert it back to RS232 again. You cannot connect to Piper straight from the network port of your workstation in the way that you do with TNC.

Pipers can also be used with one 'master' connecting to many 'slaves'. The diagram below shows the use of the modem emulation features. The computer connects to a remote unit by 'dialing' its IP number. Any number of remote devices can be controlled as required.

Another way shown below, is to use the broadcast feature. The computer sends a poll to the master Piper which broadcasts it to all the remote Pipers and their respective devices. If a remote device recognises the poll and replies, the reply is automatically sent back to the master.