How to create a virtual serial port?
grante at visi.com
Sun Apr 12 03:45:09 CEST 2009
On 2009-04-11, Dennis Lee Bieber <wlfraed at ix.netcom.com> wrote:
>> You can write a port redirector in user-space in MS-Windows,
>> but you can't in Linux/Unix. On Unix systems you have to write
>> a kernel module that sits below the tty layer. The tty layer
>> is what user applications talk to with open/close/read/write/ioctl
> Extending to the point of absurdity... Does the machine have a
> physical serial port from which the application could read?
I believe not.
> Does the machine have a USB port?
Definitely. All Mac's have had USB ports for a long, long time
> What would setting a pair of serial ports (possibly one or
> both using USB<>Serial adapters) with a null modem between
> them give?
That should work as long as the application isn't trying to do
timing-critical tricks with the modem control and status lines.
Such tricks don't work well with USB attached serial ports.
> Could the application read from one, while Python is writing
> to the other?
> Yes, it IS an absurd klutz, but...
Sadly, if a pty won't work, that's probably the easiest
solution. You can get USB-serial adapters from newegg for
under $10. For a slightly less ugly kludge, you can get a
dual-port one for $25.
And when you need to test the effects of a high-latency,
low-bandwith WAN connection on something, you can plug them
together with a null-modem cable, set them up as PPP interfaces
running at 1200 baud, and route network traffic through them.
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