Qt中TCP协议通信详解

inline qint64 QTcpSocket ::write(const QByteArray &data)

监听某个地址和端口号

bool QTcpServer::listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0);

有新的连接信号

void QTcpServer::newConnection();

是否有新的连接

virtual bool QTcpServer::hasPendingConnections() const;

获取新的连接，必须处理完才能继续接收到连接

virtual QTcpSocket *QTcpServer::nextPendingConnection();

收到新的数据信号

void QTcpSocket::readyRead();

读取收到的数据，必须读取完才能继续接收

QByteArray readAll();

使用案例（example）

客户端

#include <QTcpSocket>
#include <QWidget>
#include <QLineEdit>
class Client : public QWidget
{
    Q_OBJECT
public:
    Client(QWidget *parent);

public slots:
    void slotSendButtonClick();
private:
    QTcpSocket *_socket;
    QLineEdit *_lineEdit;
    bool _isConnected;
};

#include "client.h"
#include <QPushButton>
#include <QHBoxLayout>
Client::Client(QWidget *parent)
    : QWidget(parent)
{
    _socket = new QTcpSocket(this);

    _lineEdit = new QLineEdit(this);
    QPushButton *sendButton = new QPushButton("send");
    connect(sendButton, SIGNAL(clicked()), this, SLOT(slotSendButtonClick()));
    connect(_lineEdit, SIGNAL(returnPressed()), this, SLOT(slotSendButtonClick()));
    
    QHBoxLayout *lay = new QHBoxLayout(this);
    lay->addWidget(_lineEdit);
    lay->addWidget(sendButton);

    _isConnected = false;
}

void Client::slotSendButtonClick()
{
    if (!_isConnected)
    {
        _socket->connectToHost("127.0.0.1", 9988);
        _isConnected = true;
    }
    QString text = _lineEdit->text();
    if (!text.isEmpty())
    {
        _socket->write(text.toUtf8());//发送数据
        _lineEdit->clear();
    }
}

服务端

#include <QWidget>
#include <QTcpServer>
#include <QTcpSocket>
class QTextBrowser;
class Server :public QWidget
{
    Q_OBJECT
public:
    Server(QWidget *parent);
public slots:
    void slotCurrentIndexChanged(const QString&);
    void slotNewConnection();
private:
    QTcpServer *_server;
    QTcpSocket *_socket;
    QTextBrowser *_textBrowser;
};

#include "server.h"
#include <QHostAddress>
#include <QTextBrowser>
#include <QByteArray>
#include <QGridLayout>
#include <QNetworkInterface>
#include <QComboBox>
Server::Server(QWidget *parent)
{
    _server = new QTcpServer(this);
    //_server->listen(QHostAddress::Any, 9988);//监听跟本主机相连的所有网口
    connect(_server, SIGNAL(newConnection()),this, SLOT(slotNewConnection()) );

    QList<QHostAddress> addrList = QNetworkInterface::allAddresses();
    QComboBox *comboBox = new QComboBox;
    for (const QHostAddress& addr : addrList)
    {
        quint32 ipAddr = addr.toIPv4Address();
        if (ipAddr != 0)
        {
            comboBox->addItem(QHostAddress(ipAddr).toString());
        }
    }
    connect(comboBox, SIGNAL(currentIndexChanged(const QString&)), this, SLOT(slotCurrentIndexChanged(const QString&)));


    _textBrowser = new QTextBrowser(this);
    QGridLayout *lay = new QGridLayout(this);
    lay->addWidget(comboBox, 0, 0);
    lay->addWidget(_textBrowser,1,0);
}

void Server::slotCurrentIndexChanged(const QString& item)
{
    if (!_server->isListening())
    {
        _server->listen(QHostAddress(item), 9988);
    }
    
    _textBrowser->append("listen...");
}

void Server::slotNewConnection()
{
    _textBrowser->append("connecting...");
    while (_server->hasPendingConnections())//必须处理完所有的连接，否则有新连接时就不会在发信号过来
    {
        _socket = _server->nextPendingConnection();
        connect(_socket, &QTcpSocket::readyRead, [&]() {
            _textBrowser->append("receive message...");
            QByteArray newMessage = _socket->readAll();
            _textBrowser->append(QString(newMessage));
        });
    }
}

使用效果



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