I run a 100% off-grid site, but have a bunch of RS232 type stuff that I want to "use" in other, meaningful ways - but don't have the spare power to process it all locally.

A Lantronix 8-port terminal server works great. You can pick them up on ebay for $20 or so if you're patient.

I run my home automation (C-Bus), weather station, lightning tracker, security system, 5KW inverter and various other gear into one, the ethernet side of it connects to my microwave link back to the office, and all the 'grunt' is done there.

You can create "virtual circuits" where the RS232 on the terminal server, via whatever link connects your computer to the TS, become "invisible" to the application and they just "look like" RS232 ports on the local machine as far as the application is concerned (although I work in a unix world and choose to do it differently)

There are also plenty of single port versions (and I have three 64-port jobs as well, but they're more than a little overkill for this application!)

Give me a yell if you want more help.