Supposed you want to send async data over the IP network to another end which is also running async serial data (non-IP). A viable solution is to use udptn, which is to transport asynchronous serial data over udp.
Declare your serial interface as async
Configuring the line terminal (Enabling udptn automatically)
line 3 (depends on which line terminal is associated to your async hardware)
dispatch-timeout 1000 (in milliseconds, this means data will be sent over every 1s)
dispatch-character 13 (means data will be sent over every new line)
modem inOut (bi-directional communication)
transport output udptn (async data will be sent out using udp)
autocommand udptn 192.168.10.10 (remote ip address to be sent to)
The udptn command can only be executed in privilege exec mode, so if you want to enabling it manually:
Router# udptn 192.168.10.10 </transmit or /receive>
You can verify using your hyperterminal, whatever you type will be displayed over the other end of the hyperterminal.