Qt下應用QTcpServer與QTcpSocket實現Tcp控制

很多情形下，我們在應用程序的最外層都使用TCP作爲可靠控制，下面，我就總結一下我在項目中使用QTcpServer與QTcpSocket的一些心得和體會。

    服務端TCP程序可以利用QTcpServer，首先我們聲名QTcpServer *對象（注意：QTcpServer佔用的網絡資源需要我們手動釋放，任何我們程序可能異常退出或正常結束的地方QTcpServer *最後都要close())

    注意我們的服務端要一直監聽客戶端

   tcpPort=8888;

    tcpServer=new QTcpServer();

    if(!tcpServer->listen(QHostAddress::Any,tcpPort))

    {

        tcpServer->close();

        emit MSG(QString("listen erro"));

    }

   connect(tcpServer,&QTcpServer::newConnection,this,&TcpServer::onNewConnection);

     在新連接對應的槽裏我們把

  QTcpSocket *newpeer=tcpServer->nextPendingConnection();

   這個新連接的socket指針取下來，進行操作，當執行newpeer->write(QByterArray &MSG)即服務器向此peer發送數據；當執行QByterArray MSG=newpeer->write()即服務器讀此peer的數據，所有信息的傳遞均是對QTcpSocket的操作,並要要對每一個socket的disconnected連接deleteLater槽防止內存泄漏。

   說到此處，就牽涉到了QString 與QByterArray的轉換，因爲我們平時處理消息大多是對QSring進行處理：

   QString->QByterArray(只有英文(Latin)時)：

newpeer->write(QString("Server").toLatin1());

  QByterArray-> QString:

QTextCodec *tc= QTextCodec::codecForName("UTF-8");

QString str=tc->toUnicode((QByteArray)
rawreply)

下面的代碼抽取自 我的服務端程序

#ifndef TCPSERVER_H
#define TCPSERVER_H

#include <QObject>
#include<QTcpServer>
#include<QAbstractSocket>
class TcpServer : public QObject
{
    Q_OBJECT
public:
    explicit TcpServer(QObject *parent = 0);
    ~TcpServer();
private:
    int nb_peer;//總共的小夥伴數目，用於確定client->index的取值
    QTcpServer *tcpServer;
public slots:
    void ReadDataFromSocket();
    void onNewConnection();
    void onDisConnection();
    void processMSG(QString &MSG);
   // void processAddedClient(QTcpSocket *client);
};
#include "tcpserver.h"

TcpServer::TcpServer(QObject *parent) :
    QObject(parent),nb_peer(0)
{
    tcpPort=8888;
    tcpServer=new QTcpServer();
    if(!tcpServer->listen(QHostAddress::Any,tcpPort))
    {
        tcpServer->close();
        emit MSG(QString("listen erro"));
    }
    peerList = QList<client>();
    connect(tcpServer,&QTcpServer::newConnection,this,&TcpServer::onNewConnection);
}
void TcpServer::onNewConnection()
{

    QTcpSocket *newpeer=tcpServer->nextPendingConnection();
    //寫入驗證


    connect(newpeer,SIGNAL(readyRead()),this,SLOT(ReadDataFromSocket()));
    connect(newpeer,SIGNAL(disconnected()),newpeer,SLOT(deleteLater()));
    connect(newpeer,SIGNAL(disconnected()),this,SLOT(onDisConnection()));
    newpeer->write(QString("Server").toLatin1());
    newpeer->flush();
}
#include<QTextCodec>
#include<iterator>
void TcpServer::ReadDataFromSocket()
{
    QByteArray rawreply= static_cast<QTcpSocket*>(sender())->readAll();
    QTextCodec *tc= QTextCodec::codecForName("UTF-8");
    client beingCheckedClient;
    beingCheckedClient.index=nb_peer;
    beingCheckedClient.socket=static_cast<QTcpSocket*>(sender());
    if(tc->toUnicode(rawreply)!=QString("Client")&& !peerList.contains(beingCheckedClient
                ))
    {
        //寫入信息
        //emit ChangeLabel(QString(rawreply));
        static_cast<QTcpSocket*>(sender())->write(
                    QString("connect time out! disconnecting...").toLatin1());
        static_cast<QTcpSocket*>(sender())->flush();
        static_cast<QTcpSocket*>(sender())->disconnectFromHost();
        return ;
    }
}
TcpServer::~TcpServer()
{
    tcpServer->close();

}

客戶端就沒什麼好說的了，也是對QTcpSocket的一些操作，但是注意要在程序開始時對服務器發起連接：

    tcpsocket=new QTcpSocket();
    tcpsocket->abort();
    tcpsocket->connectToHost(("127.0.0.1"),8888);

一些問題：很多大牛可能會說，我直接使用write read接受字符串命令可能並不安全，在實際應用中我發現，低頻率的收發數據這種方法非常可靠，但是在很多客戶端同時連接時，進行回調消息驗證時，會出現信息殘缺，我的解決方案是使用延時策略，但是這並不是長久之計。

按照官方給的例子：

服務端發送數據：

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();
}

客戶端接受數據：

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);
}

缺點是每收發一回合信息，都要重連一次