Remote COM port

Two devices would remove the need for any kind of special software on windows. For the sake of the argument, make it two raspberry pis with USB to RS232 adapters.

<windows pc.com1> <--> <raspberrypi1.ttyUSB0> <--> internet via your interface of choice <raspberrypi2.ttyUSB0> <--> <proprietary equipment>

The software you want on the linux systems is socat or netcat and should be part of any modern distribution, though not installed by default. For this to work, your windows software shouldn't do anything fancy with the status lines of RS232.

Any raspberry pi is grossly oversized for the task, so feel free to search for something smaller and cheaper.

This

give some hints concerning how to use the software.

If you need to be able to set baud rates from the PC app as though it were a normal COMs port, then you need to start by finding a virtual COM driver solution and work from there. On the Linux side, connecting a tcp/ip port to a serial port should be simple - depending on your needs it can be anything from a netcat with stdio and stdout redirections, to a small server program that can handle multiple connections, multiple ports, etc.

But google first for the virtual comms port or redirector on the Windows side - that's the hard part. I'd expect the documentation for such virtual comms ports to come with suggestions for the Linux side.

Do you have a question? Why is a box needed? I've used PySerial in Python programs on Linux for stuff like that. It communicates ok with some pretty weird RS232 hardware. The details escape me but I remember I did have to patch the library for some reason. The patch was pretty simple and I believe the author merged it.

So the main problem is not provision of the internet link (which can be done a dozen ways) but conveyance of the serial port settings?

In other words, it's easy to make a transparent link that sends a fixed

115200 8N1 all day long, but what you want is to pick up that the application set it to 31250 7E2, send that message to the other end, which configures its UART to match?

In the latter case you either have to hook into the COM driver to get that information, or do some detection to try to deduce the settings of the bitstream the PC is sending you, which is potentially error prone (not sure how to tell between 7E2 and 8N2, for example).

I note that are open source virtual COM drivers like:

that has 'com2tcp' which sounds a bit like what you want. The project is ancient though, so not sure of status on modern Windows.

(once in TCP, I'd tunnel it over SSH port forwarding so you can restrict access to those with appropriate keys)

Theo

I was thinking about this solution, I see two drawbacks:

• The user PC, that is already connected to Internet, must be equipped with an additional box that must be connected to Internet

• Linux doesn't know anything about the serial port settings (baudrate, parity, and so on). The user should know the settings used by the third-party application and set them in the Linux box.

The application that opens the serial port runs on Windows and can't be changed.

Very well observed. To overcome these drawbacks, you will need two pieces of software, one on each end, that communicate the RS232 port status in addition to RX and TX. I can't help with that, since I never used or needed a virtual com port driver of that kind.

Why not use a single port terminal server, rs232 <-> lan ?. Used a lot here in the lab to get serial port kit onto the network. Typical type is the Patton 2120, though that model has probably been replaced now. Startech and Moxa build those as well, various types and capabilities, including windows port compatability

Don't need a complete system to do that, gross overkill...

Chris