使用QAbstractSocket stateChanged（） - 信号

Question

什么是QAbstractSocket stateChanged（）的正确使用/实现 - 信号？

main.cpp中：

#include <QCoreApplication>

#include <sslserver.h>
#include <QLoggingCategory>

int main(int argc, char *argv[]){

QCoreApplication a(argc, argv);
QLoggingCategory::setFilterRules("*.debug=true");

SslServer *myTestServer = new SslServer();

return a.exec();
}

SslServer.h：

#ifndef SSLSERVER_H
#define SSLSERVER_H

#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>
#include <QTimer>

class SslServer : public QObject
{
    Q_OBJECT
public:
    explicit SslServer(QObject *parent = nullptr);

private slots:
    void newTestConnection();
    void sendTestdata();
    void connectionWasClosed(QAbstractSocket::SocketState state = QAbstractSocket::UnconnectedState);

private:
    QTcpServer *testServer;
    QTcpSocket *testSocket;
    QTimer *testTimer;
};

#endif // SSLSERVER_H

SslServer.cpp：

#include "sslserver.h"
#include <QDebug>

SslServer::SslServer(QObject *parent) : QObject(parent){

    testServer = new QTcpServer(this);
    testSocket = new QTcpSocket();
    testTimer = new QTimer();

    connect(testServer, SIGNAL(newConnection()), this, SLOT(newTestConnection()));  //works
    connect(testTimer, SIGNAL(timeout()), this, SLOT(sendTestdata()));              //works
    connect(testSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(connectionWasClosed(QAbstractSocket::SocketState)));
    //Qt5 Connection was also tested, without any change to old connection-typo
    //connect(testSocket, &QAbstractSocket::stateChanged, this, &SslServer::verbindungWurdeBeendet);

    testTimer->start(1000);

    if(testServer->listen(QHostAddress::Any, 9999)){
        qDebug() << "Server running on Port 9999";
    }else{
        qDebug() << "Error while building server";
    }

}

void SslServer::newTestConnection(){
    testSocket->close();
    testSocket = testServer->nextPendingConnection();
    testSocket->write("Welcome on: Testserver!");
    testSocket->flush();

}

void SslServer::sendTestdata(){
    if(testSocket->isOpen()){
        qDebug() << testSocket->state();
        qDebug() << "Sending testdata to client";
        testSocket->write("testdata");
    }
}

void SslServer::connectionWasClosed(QAbstractSocket::SocketState){

    qDebug() << "!!! SocketState changed !!!";

}

我可以从testSocket-> state（）语句中看到状态从Unconnected变为Connected变为Unconnected，但从不调用SLOT-Function。我在这里错过了什么？

Answer 1

导致该问题是因为您正在连接到对象：

testSocket = new QTcpSocket();

但是你希望从另一个对象接收信号：

testSocket = testServer->nextPendingConnection();

解决方案是在收到新对象时建立连接：

void SslServer::newTestConnection(){
    if(testSocket)
        testSocket->close();
    testSocket = testServer->nextPendingConnection();
    connect(testSocket, &QAbstractSocket::stateChanged, this, &SslServer::connectionWasClosed);
    testSocket->write("Welcome on: Testserver!");
    testSocket->flush();
}

完整的示例可以在以下link中找到

Answer 2

你的SLOT签名与SIGNAL不匹配。

将函数声明和定义更改为

void verbindungWurdeBeendet(QAbstractSocket::SocketState state);

和连接语句

connect(testSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(verbindungWurdeBeendet(QAbstractSocket::SocketState)));

如果函数声明中有默认值，则SLOT函数verbindungWurdeBeendet()（带out参数）也是可以接受的。

例如：

在下面的例子中，你可以在SLOT语句中有一个connect，没有参数。

 void verbindungWurdeBeendet(QAbstractSocket::SocketState state = QAbstractSocket::UnconnectedState);