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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\example btchat
\title Bluetooth Chat
\meta category {Connectivity}
\brief Shows communication through Bluetooth using RFCOMM protocol.
The Bluetooth Chat example shows how to use the \l{Qt Bluetooth} API to communicate
with another application on a remote device using Bluetooth RFCOMM protocol.
\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 \c ChatServer class.
The \c ChatServer class is declared as:
\snippet btchat/chatserver.h declaration
The first thing the chat server needs to do is create an instance of
QBluetoothServer to listen for incoming Bluetooth connections. The
\c {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 system's SDP (Service
Discovery Protocol) database. The QBluetoothServiceInfo class encapsulates a service record.
We will publish a service record that contains some textual descriptions of the services, a
UUID that uniquely identifies the service, the discoverability attribute, and connection
parameters.
The textual description of the service is stored in the \c {ServiceName},
\c {ServiceDescription}, and \c {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
\l {QBluetoothUuid::}{PublicBrowseGroup}.
\snippet btchat/chatserver.cpp Service Discoverability
The \c ProtocolDescriptorList attribute is used to publish the connection parameters that the
remote device requires to connect to our service. Here we specify that the \c Rfcomm protocol
is used and set the port number to the port that our \c 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
\c {clientConnected()} slot where pending connections are connected to the
\l {QBluetoothSocket::}{readyRead()} and
\l {QBluetoothSocket::}{disconnected()} signals. The signals notify others
that a new client has connected.
\snippet btchat/chatserver.cpp clientConnected
The \c {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 \c {messageReceived()} signal.
\snippet btchat/chatserver.cpp readSocket
The \c {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 \c {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
\c rfcommServer instance is deleted.
\snippet btchat/chatserver.cpp stopServer
\section1 Chat Client
The chat client is implemented by the \c ChatClient class.
The \c 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 \c remoteService parameter. Slots are connected
to the socket's \l {QBluetoothSocket::}{readyRead()},
\l {QBluetoothSocket::}{connected()}, and
\l {QBluetoothSocket::}{disconnected()} signals.
\snippet btchat/chatclient.cpp startClient
On successful socket connection we emit a signal to notify other users.
\snippet btchat/chatclient.cpp connected
Similarly to the chat server, the \c readSocket() slot is called when data
is available from the socket. Lines are read individually and converted
from UTF-8. The \c {messageReceived()} signal is emitted.
\snippet btchat/chatclient.cpp readSocket
The \c {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
\c Chat class. This class displays a chat session between a single
\c ChatServer and zero or more \c {ChatClient}s. The \c 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 \c ChatServer and respond to its
\c {clientConnected()}, \c {clientDiconnected()}, and
\c {messageReceived()} signals.
\snippet btchat/chat.cpp Create Chat Server
In response to the \c {clientConnected()} and \c {clientDisconnected()}
signals of the \c 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 \c ChatServer are handled
in the \c {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 \c ChatClient for the service
is selected by the user.
\snippet btchat/chat.cpp Connect to remote service
In reponse to the \c {connected()} signals from \c ChatClient, we display
the "Joined chat with X." message in the chat session.
\snippet btchat/chat.cpp connected
Messages are sent to all remote devices via the \c ChatServer and
\c ChatClient instances by emitting the \c {sendMessage()} signal.
\snippet btchat/chat.cpp sendClicked
We need to clean up \c ChatClient instances when the remote device forces
a disconnect.
\snippet btchat/chat.cpp clientDisconnected
*/
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