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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt local connectivty modules.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example btchat
\title Bluetooth Chat Example
\brief An example showing communication through Bluetooth.
The Bluetooth Chat example shows how to use the \l{Qt 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.
\include examples-run.qdocinc
\section1 Chat Server
The chat server is implemented by the ChatServer class. The ChatServer class is declared as:
\snippet 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 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 btchat/chatserver.cpp Service name, description and provider
Bluetooth uses UUIDs as unique identifiers. The chat service uses a randomly generated
UUID.
\snippet btchat/chatserver.cpp Service UUID
\snippet btchat/chatserver.cpp Service UUID set
A Bluetooth service is only discoverable if it is in the PublicBrowseGroup.
\snippet 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 the port that our rfcommServer instance is listening to.
\snippet btchat/chatserver.cpp Protocol descriptor list
Finally, we register the service record with the system.
\snippet btchat/chatserver.cpp Register service
As mentioned earlier, incoming connections are handled in the clientConnected() slot where
pending connections are connected to the readyRead() and disconnected() signals. The signals
notify others that a new client has connected.
\snippet 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 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 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 btchat/chatserver.cpp sendMessage
When the chat server is stopped the service record is removed from the system SDP database, all
connected client sockets are deleted, and the QRfcommServer instance is deleted.
\snippet btchat/chatserver.cpp stopServer
\section1 Chat Client
The chat client is implemented by the ChatClient class. The ChatClient class is declared as:
\snippet btchat/chatclient.h declaration
The client creates a new QBluetoothSocket and connects to the remote service described by the
\e remoteService parameter. Slots are connected to the sockets readyRead(), connected() and
disconnected() signals.
\snippet btchat/chatclient.cpp startClient
On successful socket connection we emit a signal to notify others.
\snippet btchat/chatclient.cpp connected
Similarly 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 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 is appended.
\snippet btchat/chatclient.cpp sendMessage
To disconnect from the remote chat service, the QBluetoothSocket instance is deleted.
\snippet 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 btchat/chat.h declaration
First we construct the user interface
\snippet btchat/chat.cpp Construct UI
We create an instance of the ChatServer and respond to its clientConnected(),
clientDiconnected(), and messageReceived() signals.
\snippet btchat/chat.cpp Create Chat Server
In response to the clientConnected() and clientDisconnected() signals of the ChatServer, we
display the typical "X has joined chat." and "Y has left." messages in the chat session.
\snippet 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 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
is selected by the user.
\snippet btchat/chat.cpp Connect to remote service
In reponse to the connected() signals from ChatClient, we display the a "Joined chat with X."
message in the chat session.
\snippet btchat/chat.cpp connected
Messages are sent to all remote devices via the ChatServer and ChatClient instances by emitting
the sendMessage() signal.
\snippet btchat/chat.cpp sendClicked
We need to clean up ChatClient instances when the remote device forces a disconnect.
\snippet btchat/chat.cpp clientDisconnected
*/
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