Qt_套接字

在网上找了好多有关套接字的博客，看了一些代码，复制下来跑的时候总是不出来，然后在QDocument上找到了一个例子程序，就复制下来了。看代码的时候里面用到了好的类，好像是用来保存一个网络设置的，没看懂，然后就吧这部分给删了 = =。

运行的结果

源代码

server.h

#ifndef SERVER_H
#define SERVER_H

#include <QDialog>

class QLabel;
class QPushButton;
class QTcpServer;

class Server : public QDialog
{
    Q_OBJECT

public:
    Server(QWidget *parent = 0);

private slots:
    void sendFortune();

private:
    QLabel *statusLabel;
    QPushButton *quitButton;
    QTcpServer *tcpServer;
    QStringList fortunes;
};

#endif

server.cpp

#include <QtWidgets>
#include <QtNetwork>

#include <stdlib.h>

#include "server.h"

Server::Server(QWidget *parent)
:   QDialog(parent), tcpServer(0)
{
    statusLabel = new QLabel;
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setAutoDefault(false);

    tcpServer = new QTcpServer(this);
    if (!tcpServer->listen()) {
        QMessageBox::critical(this, tr("Fortune Server"),
                              tr("Unable to start the server: %1.")
                              .arg(tcpServer->errorString()));
        close();
        return;
    }
    QString ipAddress;
    QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();
    // use the first non-localhost IPv4 address
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (ipAddressesList.at(i) != QHostAddress::LocalHost &&
            ipAddressesList.at(i).toIPv4Address()) {
            ipAddress = ipAddressesList.at(i).toString();
            break;
        }
    }
    // if we did not find one, use IPv4 localhost
    if (ipAddress.isEmpty())
        ipAddress = QHostAddress(QHostAddress::LocalHost).toString();
    statusLabel->setText(tr("The server is running on\n\nIP: %1\nport: %2\n\n"
                            "Run the Fortune Client example now.")
                         .arg(ipAddress).arg(tcpServer->serverPort()));
    fortunes << tr("1")
             << tr("2")
             << tr("3")
             << tr("4")
             << tr("5")
             << tr("You cannot kill time without injuring eternity.")
             << tr("Computers are not intelligent. They only think they are.");

    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(sendFortune()));

    QHBoxLayout *buttonLayout = new QHBoxLayout;
    buttonLayout->addStretch(1);
    buttonLayout->addWidget(quitButton);
    buttonLayout->addStretch(1);

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(statusLabel);
    mainLayout->addLayout(buttonLayout);
    setLayout(mainLayout);

    setWindowTitle(tr("Fortune Server"));

}

void Server::sendFortune()
{
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << fortunes.at(qrand() % fortunes.size());
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));

    QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));

    clientConnection->write(block);
    clientConnection->disconnectFromHost();
}

main.cpp

#include <QApplication>
#include <QtCore>

#include <stdlib.h>

#include "server.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Server server;
    server.show();
    qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
    return app.exec();
}

client.h

#ifndef CLIENT_H
#define CLIENT_H

#include <QDialog>
#include <QTcpSocket>

class QComboBox;
class QDialogButtonBox;
class QLabel;
class QLineEdit;
class QPushButton;
class QTcpSocket;
class QNetworkSession;

class Client : public QDialog
{
    Q_OBJECT

public:
    Client(QWidget *parent = 0);

private slots:
    void requestNewFortune();
    void readFortune();
    void displayError(QAbstractSocket::SocketError socketError);

private:
    QLabel *hostLabel;
    QLabel *portLabel;
    QComboBox *hostCombo;
    QLineEdit *portLineEdit;
    QLabel *statusLabel;
    QPushButton *getFortuneButton;
    QPushButton *quitButton;
    QDialogButtonBox *buttonBox;

    QTcpSocket *tcpSocket;
    QString currentFortune;
    quint16 blockSize;

    //QNetworkSession *networkSession;
};

#endif

client.cpp

#include <QtWidgets>
#include <QtNetwork>

#include "client.h"

Client::Client(QWidget *parent)
:   QDialog(parent)
{
    hostLabel = new QLabel(tr("&Server name:"));
    portLabel = new QLabel(tr("S&erver port:"));

    hostCombo = new QComboBox;
    hostCombo->setEditable(true);
    // find out name of this machine
    QString name = QHostInfo::localHostName();
    if (!name.isEmpty()) {
        hostCombo->addItem(name);
        QString domain = QHostInfo::localDomainName();
        if (!domain.isEmpty())
            hostCombo->addItem(name + QChar('.') + domain);
    }
    if (name != QString("localhost"))
        hostCombo->addItem(QString("localhost"));
    // find out IP addresses of this machine
    QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();
    // add non-localhost addresses
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (!ipAddressesList.at(i).isLoopback())
            hostCombo->addItem(ipAddressesList.at(i).toString());
    }
    // add localhost addresses
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (ipAddressesList.at(i).isLoopback())
            hostCombo->addItem(ipAddressesList.at(i).toString());
    }

    portLineEdit = new QLineEdit;
    portLineEdit->setValidator(new QIntValidator(1, 65535, this));

    hostLabel->setBuddy(hostCombo);
    portLabel->setBuddy(portLineEdit);

    statusLabel = new QLabel(tr("This examples requires that you run the "
                                "Fortune Server example as well."));

    getFortuneButton = new QPushButton(tr("Get Fortune"));
    getFortuneButton->setDefault(true);
    getFortuneButton->setEnabled(true);
    quitButton = new QPushButton(tr("Quit"));

    buttonBox = new QDialogButtonBox;
    buttonBox->addButton(getFortuneButton, QDialogButtonBox::ActionRole);
    buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);

    tcpSocket = new QTcpSocket(this);
    connect(getFortuneButton, SIGNAL(clicked()),
            this, SLOT(requestNewFortune()));
    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    connect(tcpSocket, SIGNAL(readyRead()), this, SLOT(readFortune()));
    connect(tcpSocket, SIGNAL(error(QAbstractSocket::SocketError)),
            this, SLOT(displayError(QAbstractSocket::SocketError)));

    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->addWidget(hostLabel, 0, 0);
    mainLayout->addWidget(hostCombo, 0, 1);
    mainLayout->addWidget(portLabel, 1, 0);
    mainLayout->addWidget(portLineEdit, 1, 1);
    mainLayout->addWidget(statusLabel, 2, 0, 1, 2);
    mainLayout->addWidget(buttonBox, 3, 0, 1, 2);
    setLayout(mainLayout);

    setWindowTitle(tr("Fortune Client"));
    portLineEdit->setFocus();
}

void Client::requestNewFortune()
{
    getFortuneButton->setEnabled(false);
    blockSize = 0;
    tcpSocket->abort();
    tcpSocket->connectToHost(hostCombo->currentText(),
                             portLineEdit->text().toInt());
}

void Client::readFortune()
{
    QDataStream in(tcpSocket);
    in.setVersion(QDataStream::Qt_4_0);

    if (blockSize == 0) {
        if (tcpSocket->bytesAvailable() < (int)sizeof(quint16))
            return;

        in >> blockSize;
    }

    if (tcpSocket->bytesAvailable() < blockSize)
        return;

    QString nextFortune;
    in >> nextFortune;

    if (nextFortune == currentFortune) {
        QTimer::singleShot(0, this, SLOT(requestNewFortune()));
        return;
    }

    currentFortune = nextFortune;
    statusLabel->setText(currentFortune);
    getFortuneButton->setEnabled(true);
}

void Client::displayError(QAbstractSocket::SocketError socketError)
{
    switch (socketError) {
    case QAbstractSocket::RemoteHostClosedError:
        break;
    case QAbstractSocket::HostNotFoundError:
        QMessageBox::information(this, tr("Fortune Client"),
                                 tr("The host was not found. Please check the "
                                    "host name and port settings."));
        break;
    case QAbstractSocket::ConnectionRefusedError:
        QMessageBox::information(this, tr("Fortune Client"),
                                 tr("The connection was refused by the peer. "
                                    "Make sure the fortune server is running, "
                                    "and check that the host name and port "
                                    "settings are correct."));
        break;
    default:
        QMessageBox::information(this, tr("Fortune Client"),
                                 tr("The following error occurred: %1.")
                                 .arg(tcpSocket->errorString()));
    }

    getFortuneButton->setEnabled(true);
}

main.cpp

#include <QApplication>
#include "client.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Client client;
    client.show();
    return app.exec();
}

分析

直接从cpp文件开始看

server.cpp

server的构造函数

Server::Server(QWidget *parent)
:   QDialog(parent), tcpServer(0)
{
    //创建了一个label和按钮对象
    statusLabel = new QLabel;
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setAutoDefault(false);
    //新建一个tcpserver充当服务器
    tcpServer = new QTcpServer(this);
    //调用tcpserver的函数listen来监听是否有客户端连接，listen的第一个参数是客户端的ip地址，第二个参数是监听的端口号，若不填则为任意ip的值和一个随机的端口号
    if (!tcpServer->listen()) 
    {
        //如果没有成功监听报错并返回
        QMessageBox::critical(this, tr("Fortune Server"),
                              tr("Unable to start the server: %1.")
                              .arg(tcpServer->errorString()));
        close();
        return;
    }
    //定义了一个ip地址的链表
    //QNetworkInterface的静态方法allAddresses返回了一个ip地址的链表，里面包含了所有在这台主机上的ip地址。
    QString ipAddress;
    QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();
    //使用第一个不是本机ip的地址（并不知道是什么意思= =）
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (ipAddressesList.at(i) != QHostAddress::LocalHost &&
            ipAddressesList.at(i).toIPv4Address()) {
            ipAddress = ipAddressesList.at(i).toString();
            break;
        }
    }
    //如果没有找到就用本地主机的ipv4地址
    if (ipAddress.isEmpty())
        ipAddress = QHostAddress(QHostAddress::LocalHost).toString();
    //显示服务器的ip地址和端口号
    statusLabel->setText(tr("The server is running on\n\nIP: %1\nport: %2\n\n"
                            "Run the Fortune Client example now.")
                         .arg(ipAddress).arg(tcpServer->serverPort()));
    //将要随机显示的字符串放到字符串链表fortunes中
    fortunes << tr("1")
             << tr("2")
             << tr("3")
             << tr("4")
             << tr("5")
             << tr("You cannot kill time without injuring eternity.")
             << tr("Computers are not intelligent. They only think they are.");
    //将退出按钮的点击信号和关闭界面的槽关联起来
    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    //将新的连接信号和发送字符串的槽连接起来
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(sendFortune()));
    //设置布局管理器
    QHBoxLayout *buttonLayout = new QHBoxLayout;
    buttonLayout->addStretch(1);
    buttonLayout->addWidget(quitButton);
    buttonLayout->addStretch(1);

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(statusLabel);
    mainLayout->addLayout(buttonLayout);
    setLayout(mainLayout);
    setWindowTitle(tr("Fortune Server"));

}

发送字符串的函数

void Server::sendFortune()
{
    //定义了一个字节数组
    QByteArray block;
    //定义了一个数据流
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    //将字符链表里随机一个字符串放入到流里面
    out << fortunes.at(qrand() % fortunes.size());
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));
    //定义一个套接字用来发送这个流
    //QTcpServer的nextPendingConnection函数就就是用来返回正在与服务器相连的套接字相对应的一个套接字。
    QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));
    //将刚才的流通过套接字的write函数发送到客户端
    clientConnection->write(block);
    clientConnection->disconnectFromHost();
}

client.cpp

Client::Client(QWidget *parent)
:   QDialog(parent)
{
    //初始化两个label和一个下拉框
    hostLabel = new QLabel(tr("&Server name:"));
    portLabel = new QLabel(tr("S&erver port:"));

    hostCombo = new QComboBox;
    hostCombo->setEditable(true);
    // 找到本机的名称
    QString name = QHostInfo::localHostName();
    if (!name.isEmpty()) {
        hostCombo->addItem(name);
        QString domain = QHostInfo::localDomainName();
        if (!domain.isEmpty())
            hostCombo->addItem(name + QChar('.') + domain);
    }
    if (name != QString("localhost"))
        hostCombo->addItem(QString("localhost"));
    // 找出本机的ip地址并添加，和服务器的类似
    QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (!ipAddressesList.at(i).isLoopback())
            hostCombo->addItem(ipAddressesList.at(i).toString());
    }
    for (int i = 0; i < ipAddressesList.size(); ++i) {
        if (ipAddressesList.at(i).isLoopback())
            hostCombo->addItem(ipAddressesList.at(i).toString());
    }

    portLineEdit = new QLineEdit;
    portLineEdit->setValidator(new QIntValidator(1, 65535, this));

    hostLabel->setBuddy(hostCombo);
    portLabel->setBuddy(portLineEdit);

    statusLabel = new QLabel(tr("This examples requires that you run the "
                                "Fortune Server example as well."));

    getFortuneButton = new QPushButton(tr("Get Fortune"));
    getFortuneButton->setDefault(true);
    getFortuneButton->setEnabled(true);
    quitButton = new QPushButton(tr("Quit"));

    buttonBox = new QDialogButtonBox;
    buttonBox->addButton(getFortuneButton, QDialogButtonBox::ActionRole);
    buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);

    //初始化套接字，用于和主机通讯
    tcpSocket = new QTcpSocket(this);
    //将点击按钮和获得字符串关联起来
    connect(getFortuneButton, SIGNAL(clicked()),
            this, SLOT(requestNewFortune()));
    //将退出按钮和关闭窗口关联起来
    connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
    //将套接字的获取到新的数据流信号和读取数据槽关联起来
    connect(tcpSocket, SIGNAL(readyRead()), this, SLOT(readFortune()));
    //将套接字的错误与错误函数关联起来
    connect(tcpSocket, SIGNAL(error(QAbstractSocket::SocketError)),
            this, SLOT(displayError(QAbstractSocket::SocketError)));

    //设置布局管理器
    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->addWidget(hostLabel, 0, 0);
    mainLayout->addWidget(hostCombo, 0, 1);
    mainLayout->addWidget(portLabel, 1, 0);
    mainLayout->addWidget(portLineEdit, 1, 1);
    mainLayout->addWidget(statusLabel, 2, 0, 1, 2);
    mainLayout->addWidget(buttonBox, 3, 0, 1, 2);
    setLayout(mainLayout);

    setWindowTitle(tr("Fortune Client"));
    portLineEdit->setFocus();
}

requestnewfortune函数

void Client::requestNewFortune()
{
    //初始化数据块大小的值
    blockSize = 0;
    //终止当前的连接并重置套接字
    tcpSocket->abort();
    //连接到主机，如果找到主机名称，套接字就会发出找到hostFound()信
    //号并开始连接，如果连接成功就会发出connected()信号并进入连接状态
    tcpSocket->connectToHost(hostCombo->currentText(),
                             portLineEdit->text().toInt());
}

读取字符串函数

void Client::readFortune()
{
    //qt中的套接字继承了QIODevice，所以可以类似于读取文件的方式来读取内容
    QDataStream in(tcpSocket);
    in.setVersion(QDataStream::Qt_4_0);
    //bytesAvailable()函数是返回套接字中数据流的大小
    if (blockSize == 0) {
        if (tcpSocket->bytesAvailable() < (int)sizeof(quint16))
            return;

        in >> blockSize;
    }

    if (tcpSocket->bytesAvailable() < blockSize)
        return;
    //将套接字中的内容写入到字符串中
    QString nextFortune;
    in >> nextFortune;

    if (nextFortune == currentFortune) {
        QTimer::singleShot(0, this, SLOT(requestNewFortune()));
        return;
    }

    currentFortune = nextFortune;
    statusLabel->setText(currentFortune);
}