I've used serial terminal servers for a long time. Basically, these are devices that allow you to communicate with a serial (eg RS232/RS485/RS422) device over ethernet in various ways. Folks in this community may typically use these things as secondary communication channels for network equipment management. My use case is setting up automated manufacturing facilities where the devices being manufactured are tested/configured using a serial connection. A server-based application can then "talk" to many devices through one or more terminal servers.
For example, with a Perle terminal server (like this), I can connect to multiple serial devices and communicate to them using an SSH client. From the point of view of my manufacturing test applications, I can send and receive data to the serial console of each device using an SSH connection. From the point of view of the device, it just sends/receives serial data without knowing anything about the ethernet connection.
This works great. It means I can create manufacturing test systems whose applications run on servers in a datacenter and the devices under test just need a robust inexpensive terminal server on the test-jig. No flaky COM-ports, no flimsy station PC's needed. This can scale smoothly to many simultaneous devices under test depending on how beefy the server is. Points of failure are minimal. And things like failing-over, updates and maintenance are relatively straightforward.
BUT NOW, more and more devices use a USB connection. Inside, there's actually something like an FDTI chip-- so it goes to serial eventually, but I may not be able to get to it. And actually, I may need to use the USB connection anyway for the purpose of testing functionality.
The problem is I can't find "terminal servers" that allow me to, say, connect 16 devices which use a "serial-over-USB" connection. It is looking like my only choice is to connect them to a USB-hub and connect the HUB to a PC over USB. I'd rather NOT do that because then I can't trivially reuse my existing applications that talk over an SSH connection and I have to "re-tool" them to use COM ports. Moreover, it seems, I now have to set-up actual PC's at device-testing stations. I much prefer the really tough terminal servers.
One would think that such a serial terminal would exist-- I can't find one. Why is that? Could I be using the wrong terminology in searching for it? Are there alternative robust and scaleable solutions to consider for accomplishing this?