I'm learning how to use the Arduino HC-05 Bluetooth module. After pairing to it with my laptop I saw that I was getting two serial links, COM4 and COM5, as can be seen from the picture below.

On COM4 everything is working fine, but on COM5 nothing is happening. Can somebody explain why this is so?

NOTE: I only have one Bluetooth device (the HC-05).

enter image description here

  • 1
    You didn't include a picture in your question
    – chrisl
    Dec 14, 2021 at 16:15
  • your question is not arduino specific ... it belongs at stackoverflow.com/questions
    – jsotola
    Dec 14, 2021 at 16:40
  • @chrisl sorry i forgot
    – Kennerdol
    Dec 14, 2021 at 18:19
  • @jsotola i chose that because its what am working with but all in all thank you.
    – Kennerdol
    Dec 14, 2021 at 18:22
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    @jsotola they do, I have tried to uninstall both of them but once I just pair to the module they both appear. Am preparing to try on Ubuntu 20.04LTS and see what happens
    – Kennerdol
    Dec 14, 2021 at 19:31

1 Answer 1


I found this answer in Microsoft Technet helpful:

  • when connecting your terminal program to the first you are actually instructing Windows to attempt to establish the Bluetooth connection to the remote paired device, and if the connection is established the RFCOMM channel will be opened for the exchange of data
  • when connecting your terminal program to the second you are actually instructing Windows to load the SPP SDP record and to remain waiting for incoming connections from the remote paired device.

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