Can 2 apps use same serial port

[Me]

Is it possible to use a already openned serial port?
I need to be able to have two applications running and both use the same
serial port. Is this possible & how can I do it.

[ScottMcP [MVP]]

Is it possible to use a already openned serial port? I need to be able to have two applications running and both use the same serial port. Is this possible & how can I do it.

It is not possible for two apps to open a serial port simultaneously. The only possible approach is to have an app that opens the port and provides some form of interprocess communication that the other app can use.

If you only need read access to the port you can build a splitter cable that feeds received data into two ports.

[Me]

Then how do serial port monitors work?
They are apparently able use the same port as another application!

Post by ScottMcP [MVP]

Is it possible to use a already openned serial port? I need to be able to have two applications running and both use the same serial port. Is this possible & how can I do it.

It is not possible for two apps to open a serial port simultaneously. The only possible approach is to have an app that opens the port and provides some form of interprocess communication that the other app can use.
If you only need read access to the port you can build a splitter cable that feeds received data into two ports.

[ScottMcP [MVP]]

Then how do serial port monitors work? They are apparently able use the same port as another application!

They use a customized device driver. You can do anything you want if you write your own device driver.