Qt文档阅读笔记-Simple Chat Example解析

x33g5p2x  于2022-06-06 转载在 其他  
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这个实例使用QWebSocket和QWebSocketServer去构造WebSocket协议的极简聊天室。

官方对于这个实例给出的文档方面的介绍就这么多,下面是对应的代码,我自己补充下:

文件一共如下:

我们由简入深分析下,首先是simplechat.pro

QT = websockets

 TARGET = chatserver
 CONFIG   += console
 CONFIG   -= app_bundle

 TEMPLATE = app

 SOURCES += \
     main.cpp \
     chatserver.cpp

 HEADERS += \
     chatserver.h

 EXAMPLE_FILES += chatclient.html

 target.path = $$[QT_INSTALL_EXAMPLES]/websockets/simplechat
 INSTALLS += target

这里主要是包含websockets模块,使用的语法是 QT = websockets

main.cpp就是实例化ChatServer在此不再说明。

下面是chartserver.h和chartserver.cpp

#ifndef CHATSERVER_H
#define CHATSERVER_H

#include <QtCore/QObject>
#include <QtCore/QList>

QT_FORWARD_DECLARE_CLASS(QWebSocketServer)
QT_FORWARD_DECLARE_CLASS(QWebSocket)
QT_FORWARD_DECLARE_CLASS(QString)

class ChatServer : public QObject
{
    Q_OBJECT
public:
    explicit ChatServer(quint16 port, QObject *parent = nullptr);
    ~ChatServer() override;

private slots:
    void onNewConnection();
    void processMessage(const QString &message);
    void socketDisconnected();

private:
    QWebSocketServer *m_pWebSocketServer;
    QList<QWebSocket *> m_clients;
};

#endif //CHATSERVER_H
#include "chatserver.h"

#include <QtWebSockets>
#include <QtCore>

#include <cstdio>
using namespace std;

QT_USE_NAMESPACE

static QString getIdentifier(QWebSocket *peer)
{
    return QStringLiteral("%1:%2").arg(peer->peerAddress().toString(),
                                       QString::number(peer->peerPort()));
}

//! [constructor]
ChatServer::ChatServer(quint16 port, QObject *parent) :
    QObject(parent),
    m_pWebSocketServer(new QWebSocketServer(QStringLiteral("Chat Server"),
                                            QWebSocketServer::NonSecureMode,
                                            this))
{
    if (m_pWebSocketServer->listen(QHostAddress::Any, port))
    {
        QTextStream(stdout) << "Chat Server listening on port " << port << '\n';
        connect(m_pWebSocketServer, &QWebSocketServer::newConnection,
                this, &ChatServer::onNewConnection);
    }
}

ChatServer::~ChatServer()
{
    m_pWebSocketServer->close();
}
//! [constructor]

//! [onNewConnection]
void ChatServer::onNewConnection()
{
    auto pSocket = m_pWebSocketServer->nextPendingConnection();
    QTextStream(stdout) << getIdentifier(pSocket) << " connected!\n";
    pSocket->setParent(this);

    connect(pSocket, &QWebSocket::textMessageReceived,
            this, &ChatServer::processMessage);
    connect(pSocket, &QWebSocket::disconnected,
            this, &ChatServer::socketDisconnected);

    m_clients << pSocket;
}
//! [onNewConnection]

//! [processMessage]
void ChatServer::processMessage(const QString &message)
{
    QWebSocket *pSender = qobject_cast<QWebSocket *>(sender());
    for (QWebSocket *pClient : qAsConst(m_clients)) {
        if (pClient != pSender) //don't echo message back to sender
            pClient->sendTextMessage(message);
    }
}
//! [processMessage]

//! [socketDisconnected]
void ChatServer::socketDisconnected()
{
    QWebSocket *pClient = qobject_cast<QWebSocket *>(sender());
    QTextStream(stdout) << getIdentifier(pClient) << " disconnected!\n";
    if (pClient)
    {
        m_clients.removeAll(pClient);
        pClient->deleteLater();
    }
}
//! [socketDisconnected]

这里解释几个点:

①m_pWebSocketServer是QWebSocketServer,指定其名和mode以及开通的端口号;

②newConnection中,使用m_pWebSocketServer获取nextPendingConnection,然后得到这个与客户端相连的socket后,设置信号与槽。

③processMessage,将获取到用户发来的信号与槽,发送给所有连接到服务器的用户。

④socketDisconnect,当用户断开连接后,把其用户移除m_clients。

下面是chartclient.html

<html>
    <head>
        <title>WebSocket Chat Client</title>
    </head>
    <body>
        <h1>WebSocket Chat Client</h1>
        <p>
            Host: <input id="webSocketHost" type="text" value="localhost:1234"/>
        </p>
        <p>
            <button onClick="initWebSocket();">Connect</button>
            <button id="disconnectButton" onClick="stopWebSocket();" disabled>Disconnect</button>
            <button onClick="checkSocket();">State</button>
        </p>
        <p>
            <textarea id="debugTextArea" style="width:400px;height:200px;" readonly></textarea>
        </p>
        <p>
            <input type="text" id="inputNick" value="nickname" />
            <input type="text" id="inputText" onkeydown="if(event.keyCode==13)sendMessage();"/>
            <button id="sendButton" onClick="sendMessage();" disabled>Send</button>
        </p>

        <script type="text/javascript">
            var debugTextArea = document.getElementById("debugTextArea");
            function debug(message) {
                debugTextArea.value += message + "\n";
                debugTextArea.scrollTop = debugTextArea.scrollHeight;
            }

            function sendMessage() {
                var nickname = document.getElementById("inputNick").value;
                var msg = document.getElementById("inputText").value;
                var strToSend = nickname + ": " + msg;
                if ( websocket != null )
                {
                    document.getElementById("inputText").value = "";
                    websocket.send( strToSend );
                    console.log( "string sent :", '"'+strToSend+'"' );
                    debug(strToSend);
                }
            }

            var websocket = null;

            function initWebSocket() {
                try {
                    if (typeof MozWebSocket == 'function')
                        WebSocket = MozWebSocket;
                    if ( websocket && websocket.readyState == 1 )
                        websocket.close();
                    var wsUri = "ws://" + document.getElementById("webSocketHost").value;
                    websocket = new WebSocket( wsUri );
                    websocket.onopen = function (evt) {
                        debug("CONNECTED");
                        document.getElementById("disconnectButton").disabled = false;
                        document.getElementById("sendButton").disabled = false;
                    };
                    websocket.onclose = function (evt) {
                        debug("DISCONNECTED");
                        document.getElementById("disconnectButton").disabled = true;
                        document.getElementById("sendButton").disabled = true;
                    };
                    websocket.onmessage = function (evt) {
                        console.log( "Message received :", evt.data );
                        debug( evt.data );
                    };
                    websocket.onerror = function (evt) {
                        debug('ERROR: ' + evt.data);
                    };
                } catch (exception) {
                    debug('ERROR: ' + exception);
                }
            }

            function stopWebSocket() {
                if (websocket)
                    websocket.close();
            }

            function checkSocket() {
                if (websocket != null) {
                    var stateStr;
                    switch (websocket.readyState) {
                        case 0: {
                            stateStr = "CONNECTING";
                            break;
                        }
                        case 1: {
                            stateStr = "OPEN";
                            break;
                        }
                        case 2: {
                            stateStr = "CLOSING";
                            break;
                        }
                        case 3: {
                            stateStr = "CLOSED";
                            break;
                        }
                        default: {
                            stateStr = "UNKNOW";
                            break;
                        }
                    }
                    debug("WebSocket state = " + websocket.readyState + " ( " + stateStr + " )");
                } else {
                    debug("WebSocket is null");
                }
            }
        </script>
    </body>
</html>

这个html代码,浏览器运行后,会创建一个websocket连接到服务端上,然后进行文本串的交互。

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