Sharing USB / COM 3 port

[JBrondos]

Simplify3D reports an error message when trying to add machine for direct printing via USB.

I get the following error message when I try to connect:

Attempting connection at \\.\COM3...
Permissions error connecting to port
Is there another application already connected to this port?
Error opening selected port.

This happens even if I don't have any other 3D printer applications running -- and I don't know of anything else trying to use the COM 3 port.

I do, however, have some other 3d print programs _installed_: Makerbot Desktop, Cura, ReplicatorG.

The Makerbot Desktop IS able to print directly, but none of the others. I thought I'd check selective startup to see if Makerbot was assigning the COM port at boot, but I didn't see it there.

[CompoundCarl]

You can't share a COM port. If one program is already using it, no other programs will be able to connect.

MakerBot desktop has a background service that will constantly use your COM ports. It's super annoying. You can stop it by opening MakerBot Desktop and then going to Services > Stop Background Service. But unfortunately, the smart people at MakerBot made it so that anytime you restart your computer, this service will turn on again. So you have to stop it every time you turn on your computer.

For me, I just uninstalled their bloated software

[JBrondos]

<< For me, I just uninstalled their bloated software [/quote]>>

This was helpful. I uninstalled the Makerbot program and uninstalled the two COM drivers in Device Manager. Now my other programs can access the COM port.