Connect to external device via bluetooth. Who's master/slave? 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.

Question

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".
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.