A bit of background first: the distinction between incoming and outgoing RFCOMM (Bluetooth stack protocol for virtual COMs) ports is necessary because it's always one of the communicating devices that initiates the connection (a bit similar to TCP sockets - where you have server and client).
- The outgoing COM port is used when the PC initiates the connection to the
remote device (opening the port initiates RFCOMM connection to the remote device).
- The incoming COM port is used when the remote device initiates the
connection.
Once the connection is opened it is bidirectional, regardless of the type.
That said, this Bluetooth module supports both master and slave mode (see manual chapter 2), that's why it advertises 2 RFCOMM/SPP ports, I guess. If you want PC to initiate the connection, use COM6, otherwise use COM7.
Why you see no echo in PuTTY? By default there's no local echo, and you actually shouldn't see any characters you type (unless you short UART_RX to UART_TX, or have some real device attached there to communicate with). The module itself is transparent (in the data mode, that is).
Also, baud rate etc. shouldn't really matter for Blueooth connection - note, that chapter 3.2 refers to configuring the device via physical serial port (UART_RX/TX pins, i.e. from the device side), while 3.3 describes configuring over virtual port (i.e. from the PC side). I somehow feel you're confusing the module sides ;)
This excerpt from the manual is quite important:
To connect to FireFly, browse for
services, you should see: “SPP”
profile with a virtual COM port. Open
this virtual COM port to create a
Bluetooth connection. Once connected,
the device will be in data mode
allowing data to flow in both
directions as if the serial port were
locally attached to the PC. The device
must be in command mode for
configuration and programming. To
enter command mode type “$$$” (three
dollar signs) from either the remote
Bluetooth connection or the local
serial port connection. You must enter
command mode within 60 seconds
(configurable by setting the config
timer).
Cool module, btw!
Check the Cobra Tags FAQ
Answer to first and second question.
Can I use a Cobra or other manufacturer’s Bluetooth headset for
handsfree talking while using this product?
Yes you can. The Cobra Tag uses a different Bluetooth communication
link than the headsets (called serial port profile) so they can both
work together.
How many Cobra Tags can be connected to one mobile phone?
The maximum number with some phones is 7. The maximum number that can
be paired with iOS devices is 1. This is based on a technology
limitation. It seems that some phones can’t simultaneously handle 7
Tags and are better off with 1-5 maximum.
Answer to Third question.
SPP emulates a serial cable to provide a simple substitute for existing RS-232. Architecture of cobra tag shows it doesn't need complex data manipulation and just requires a few set of commands for its operation. I'll suggest sticking to this profile only.
Best Answer
"Server" devices are usually characterized by having data that is needed by some other device. A temperature sensor for example has information that others may wish to know. "Server" devices may also be capable of taking actions upon request or storing information for later use.
"Client" devices are the other half of the puzzle. A "client" may be a device that needs information from a server. It may also be the device that commands the heating and cooling system into the requested mode, or provides the set points to allow the system to operate automatically.
Source: Introduction to Bluetooth Application Development
Bluetooth networks (commonly referred to as piconets) use a master/slave model to control when and where devices can send data. In this model, a single master device can be connected to up to seven different slave devices. Any slave device in the piconet can only be connected to a single master.
The master coordinates communication throughout the piconet. It can send data to any of its slaves and request data from them as well. Slaves are only allowed to transmit to and receive from their master. They can’t talk to other slaves in the piconet.
Bluetooth Basics