使用qabstractsocket statechanged(） - 信号

Use of QAbstractSocket stateChanged()-Signal

本文关键字：信号 qabstractsocket statechanged 使用      更新时间：2023-10-16

qabstractsocket statechanged（）的正确使用/实现是什么？signal ？

main.cpp：

#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，该状态正在从未连接 connected connected ，但是插槽功能从未被调用。我在这里缺少什么？

问题是由于您连接到对象而引起的：

testSocket = new QTcpSocket();

，但您希望从另一个对象接收信号：

testSocket = testServer->nextPendingConnection();

收到新对象时，解决方案是建立连接：

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

可以在以下链接

中找到完整的示例

您的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)));

SLOT函数 verbindungWurdeBeendet()（带有参数）也可以接受，如果您在函数声明中具有默认值。

ex：

在下面的情况下，您可以在connect语句中使用SLOT，而无需参数。

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