Question: I have various devices to connect to my iMac using good-old RS-232.

Of course, I only have USB connectors on my machine.

I have a couple of Prolific PL2303-based cables, and they seem to work OK, but the kext provided seems a little flaky and I'm not sure about long-term support.

What is the most-stable, best-supported USB-Serial chip-set or cable?

Answer: 
Just to be clear, **I have not used this device myself.**

Stewart Cheshire, creator of ZeroConf (the basis of Bonjour), gave a Google Tech Talk on the subject of ZeroConf, and presented a couple of embedded devices (Cameras, and an RS-232 unit).

I've always wanted to try this out, but have never had a good enough use to cough up the money to do so.

Stewart presented an RS-232 over Ethernet module from [SitePlayer](http://netmedia.com/siteplayer/telnet/index.html). They have a built in web interface used to set up the ethernet and serial parameters, and if I understand correctly, you simply telnet to the device's IP address in order to be presented with the serial interface. (See their [pdf](http://netmedia.com/siteplayer/telnet/documents/SitePlayer%20Telnet.pdf) on the subject.)
I'm professionaly using a
[Roline USB to Serial 0.3 m long adapter](http://shop.roline.com/roline_converter_cable_usb_to_serial_0_3_m/12.02.1089-20.html?t_Action=searchKatalog&t_SearchValue=&t_Sort=&manufacturer=&device=&t_Hier=&t_SubHier=&t_lager=&t_CatID=3078&t_ParentID=3077).
I'm using the [PL2303 OSX driver](http://sourceforge.net/projects/osx-pl2303/).

When I plug my cable, this driver dynamically create `/dev/tty.PL2303-0000nnnn`. I use it from a `Terminal` or `xterm` window with:
`screen /dev/tty.PL2303-0000nnnn`.

0 problem with hundreds of connections on network equipments and servers (Brocade, Cisco, Extreme, Oracle (ex. Sun)…).