Quick intro:

We have an external device (it's not android) that we usually connect to PCs via Serial Port->USB converter. But now we want to use also Android tablets to send commands to that external device so we are going to add a bluetooth module that can act as a bridge between the device's Serial Port and Android tablets.


Should we buy a slave bluetooth module or a master one?
The external device is like a "server" that is always working, and the PC/tablet just connects and sends commands to it.

Master means "server" or "client"? It's a bit confusing cause the Android doc uses "server/client" terminology while hardware stores use "master/slave".

  • 1
    As almost all of the "master" BT modules can work also as slave (there are "master/slave" and "slave" modules, but not "master" only) I think master means server or host but I'm not 100% sure. Commented Apr 8, 2013 at 7:04

1 Answer 1


I think master means server or host but I'm not 100% sure.

It's not correct. For android device, master means client and slave means server. Slave device should always [Inquiry Scan] to wait for [Inquiry] which send by master. When slave get [Inquiry], it will send FHS packet to master. And then slave begin to [Page Scan], and master begin to [Page] to slave to complete the connection.

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    Is it correct that in Android nearby.connections API, the one doing the startAdvertising is the master? And the one doing the startDiscovery is the slave?
    – daparic
    Commented Nov 19, 2021 at 2:34

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