At the moment you can use a MOXA LAN to RS232 converter model DE311. You can then establish a TCP/IP connection to the PLC. Other RS232 to LAN converter can also be used.
TRi plans to introduce a Ethernet to RS232 converter in 1st quarter 2004 that will incorporate a subset of the TLServer functionality so that one or multiple M-series PLC may be accessed on the LAN without the need for a PC to host the TLServer. Look out for the announcement 1Q next year.