For OBEX servers: This defines the server channel on which the OBEX server listens for connections. The server channel is set using SetPort on the TRfcommSockAddr. Note: 1) Unless the channel is defined as KRfcommPassiveAutoBind it may be in use when the obex server attempts to 'bind' to it 2) If the channel is defined as KRfcommPassiveAutoBind then when the server is FIRST started it will attempt to find a free RFComm channel. If this is successful that free channel will be used as the server channel for the life time of the obex server including when it is 'stopped' and re-'started'. 3) When the obex server is stopped, and very briefly when a bluetooth connection comes down, the obex server releases its server channel. It is possible therefore that during this time another application might bind to it. This will cause an error when the obex server tries to re-bind.

Also note that a Bluetooth OBEX server will itself set the Object Transfer bit in the Service Class as required by the Generic Object Exchange Profile so the user need not do this. CObexServer

For OBEX clients: This defines the server channel and the device address to connect to. The server channel and device address are set respectively using SetPort and SetBTAddr on the TRfcommSockAddr.