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/*!
    \example btchat
    \title Bluetooth Chat Example

    The Bluetooth Chat example shows how to use the Qt Connectivity Bluetooth API to communicate
    with another application on a remote device using Bluetooth.

    \image btchat-example.png

    The Bluetooth Chat example implements a simple chat program between multiple parties.  The
    application always acts as both a server and a client eliminating the need to determine who
    should connect to whom.

    \section1 Chat Server

    The chat server is implemented by the ChatServer class.  The ChatServer class is declared as:

    \snippet examples/btchat/chatserver.h declaration

    The first thing the chat server needs to do is create an instance of QRfcommServer to listen
    for incoming Bluetooth connections.  Our clientConnected() slot will be called whenever a new
    connection is created.

    \snippet examples/btchat/chatserver.cpp Create the server

    The chat server is only useful if others know that it is there.  To enable other devices to
    discover it a record describing the service needs to be published in the systems SDP (Service
    Discovery Protocol) database.  The QBluetoothServiceInfo class encapsulates a service record.

    We will publish a service record that contains some textural descriptions of the services, a
    UUID that uniquely identifies the service, the discoverability attribute and connection
    parameters.

    The textural description of the service is stored in the ServiceName, ServiceDescription and
    ServiceProvider attributes.

    \snippet examples/btchat/chatserver.cpp Service name, description and provider

    Bluetooth uses UUIDs as unique identifiers.  Our chat service is uses a randomly generated
    UUID.

    \snippet examples/btchat/chatserver.cpp Service UUID
    \snippet examples/btchat/chatserver.cpp Service UUID set

    A Bluetooth service is only discoverable if it is in the PublicBrowseGroup.

    \snippet examples/btchat/chatserver.cpp Service Discoverability

    The ProtocolDescriptorList attribute is used to publish the connection parameters that the
    remote device requires to connect to our service.  Here we specify that the Rfcomm protocol is
    used and set the port number to port that our rfcommServer instance is listening to.

    \snippet examples/btchat/chatserver.cpp Protocol descriptor list

    Finally we register the service record with the system.

    \snippet examples/btchat/chatserver.cpp Register service

    As mentioned earlier incoming connections are handled in the clientConnected() slot.  In this
    slot we get a pointer a QBluetoothSocket representing the next pending connection connect up
    slots to the readyRead() and disconnected() signals and emit a signal to notify others that a
    new client has connected.

    \snippet examples/btchat/chatserver.cpp clientConnected

    The readSocket() slot is called whenever data is ready to be read from a client socket.  The
    slot reads individual lines from the socket converts them from UTF-8 and emits the
    messageReceived() signal.

    \snippet examples/btchat/chatserver.cpp readSocket

    The clientDisconnected() slot is called whenever a client disconnects from the service.  The
    slot emits a signal to notify others that a client has disconnected and deletes the socket.

    \snippet examples/btchat/chatserver.cpp clientDisconnected

    The sendMessage() slot is used to send a message to all connected clients.  The message is
    converted into UTF-8 and appended with a newline before being sent to all clients.

    \snippet examples/btchat/chatserver.cpp sendMessage

    When the chat server is stop the service record is removed from the system SDP database, all
    connected client sockets are deleted and the QRfcommServer instance is deleted.

    \snippet examples/btchat/chatserver.cpp stopServer

    \section1 Chat Client

    The chat client is implemented by the ChatClient class.  The ChatClient class is declared as:

    \snippet examples/btchat/chatclient.h declaration

    The client creates a new QBluetoothSocket and connects to the remote service described by the
    \i remoteService parameter.  Slots are connected to the sockets readyRead(), connected() and
    disconnected() signals.

    \snippet examples/btchat/chatclient.cpp startClient

    On sucessfull socket connection we emit a signal to notify other.

    \snippet examples/btchat/chatclient.cpp connected

    Similarily to the chat server the readSocket() slot is called when data is available from the
    socket.  Lines are read individually and converted from UTF-8.  The messageReceived() signal
    is emitted.

    \snippet examples/btchat/chatclient.cpp readSocket

    The sendMessage() slot is used to send a message to the remote device.  The message is
    converted to UTF-8 and a newline appended.

    \snippet examples/btchat/chatclient.cpp sendMessage

    To disconnect from the remote chat service the QBluetoothSocket instance is deleted.

    \snippet examples/btchat/chatclient.cpp stopClient

    \section1 Chat Dialog

    The main window of this example is the chat dialog, implemented in the Chat class.  This class
    displays a chat session between a single ChatServer and zero or more ChatClients.  The Chat
    class is declared as:

    \snippet examples/btchat/chat.h declaration

    First we construct the user interface

    \snippet examples/btchat/chat.cpp Construct UI

    We create an instance of the ChatServer and respond to its clientConnected(),
    clientDiconnected() and messageReceived() signals.

    \snippet examples/btchat/chat.cpp Create Chat Server

    In response to the clientConnected() and clientDisconnected() signals of the ChatServer we
    display the typical "foo has joined chat." and "foo has left." messages in the chat session.

    \snippet examples/btchat/chat.cpp clientConnected clientDisconnected

    Incoming messages from clients connected to the ChatServer are handled in the showMessage()
    slot.  The message text tagged with the remote device name is displayed in the chat session.

    \snippet examples/btchat/chat.cpp showMessage

    In response to the connect button being clicked the application starts service discovery and
    presents a list of discovered chat services on remote devices.  A ChatClient for the service
    selected by the user.

    \snippet examples/btchat/chat.cpp Connect to remote service

    In reponse to connected() signals from ChatClient we display the a "Joined chat with foo."
    message in the chat session.

    \snippet examples/btchat/chat.cpp connected

    Messages are sent to all remote devices via the ChatServer and ChatClient instances by emitting
    the sendMessage() signal.

    \snippet examples/btchat/chat.cpp sendClicked

    We need to clean up ChatClient instances when the remote device forces a disconnect.

    \snippet examples/btchat/chat.cpp clientDisconnected
*/
