[英]QObject: no such slot QThread::readyRead()
I am trying to figure out how to correctly use Qt TCP Sockets, as well as multithreading. 我试图弄清楚如何正确使用Qt TCP套接字以及多线程。 I want, as a test project in support of something more complex but similar I will try in the future, to do the following: a simple application that either listens for exactly one incoming connection, or connects to a serversocket;
作为一个支持更复杂但又相似的项目的测试项目,我希望将来做以下工作:一个简单的应用程序,要么只监听一个传入连接,要么连接到服务器插槽; next it prints everything it receives over that socket.
接下来,它将打印通过该套接字接收到的所有内容。
The situation where I connect to a serversocket (I use netcat with the -l option for this) works fine: everything netcat sends to my application is printed correctly. 我连接到serverocket的情况(我将netcat与-l选项一起使用)工作正常:将netcat发送到我的应用程序的所有内容均正确打印。 However, when I use my program to listen for that one incoming connection (generated by netcat), the connecting succeeds but then I get this runtime error:
但是,当我使用程序侦听该传入连接(由netcat生成)时,连接成功,但随后出现此运行时错误:
QObject::connect: No such signal QThread::readyRead() in ..\QTcpTest\listener.cpp:8
Here is the entire code (don't mind the plain CI/OI use sometimes, I'll remove this later): 这是完整的代码(不要介意有时会使用普通的CI / OI,稍后再删除):
[ main.cpp ] [main.cpp]
#include "peer.h"
#include <QCoreApplication>
#include <QThread>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static bool askIfServer();
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
Peer *p;
int rval;
if (askIfServer())
p = new Peer;
else
p = new Peer(false);
rval = a.exec();
delete p;
return rval;
}
static bool askIfServer()
{
bool isServer;
char ibuf[BUFSIZ];
fputs("Choose \'host\' or \'join\': ", stderr);
fgets(ibuf, BUFSIZ, stdin);
ibuf[strlen(ibuf) - 1] = '\0';
fflush(stdin);
if (strcmp(ibuf, "host") == 0)
isServer = true;
else if (strcmp(ibuf, "join") == 0)
isServer = false;
else
{
fputs("Failure.\n", stderr);
exit(-1);
}
return isServer;
}
[ peer.h ] [peer.h]
#ifndef PEER_H
#define PEER_H
#include "listener.h"
#include <QObject>
#include <QThread>
#include <QtNetwork/QTcpSocket>
#include <QtNetwork/QTcpServer>
class Peer : public QObject
{
Q_OBJECT
public:
static const quint16 PORT = 5483;
explicit Peer(bool isHost = true, QString hostname = "localhost", QObject *parent = 0);
public slots:
void acceptPeer();
private:
bool _isHost;
QTcpServer *_server;
QTcpSocket *_socket;
QThread *_lThread;
Listener *_listener;
};
#endif // PEER_H
[ peer.cpp ] [peer.cpp]
#include "peer.h"
Peer::Peer(bool isHost, QString hostname, QObject *parent) :
QObject(parent),
_isHost(isHost)
{
if (_isHost)
{
_server = new QTcpServer;
connect(_server, SIGNAL(newConnection()), this, SLOT(acceptPeer()));
_server->listen(QHostAddress::Any, PORT);
}
else
{
_socket = new QTcpSocket;
connect(_socket, SIGNAL(hostFound()), this, SLOT(acceptPeer()));
_socket->connectToHost(hostname, PORT);
}
}
void Peer::acceptPeer()
{
disconnect(this, SLOT(acceptPeer()));
if (_isHost)
{
_socket = _server->nextPendingConnection();
delete _server;
_server = NULL;
}
_lThread = new QThread;
_listener = new Listener(_socket);
_listener->moveToThread(_lThread);
_lThread->start();
}
[ listener.h ] [listener.h]
#ifndef LISTENER_H
#define LISTENER_H
#include <iostream>
#include <QObject>
#include <QByteArray>
#include <QtNetwork/QTcpSocket>
using std::cout;
class Listener : public QObject
{
Q_OBJECT
public:
explicit Listener(QTcpSocket *socket, QObject *parent = 0);
public slots:
void acceptData();
private:
QTcpSocket *_socket;
};
#endif // LISTENER_H
[ listener.cpp ] [listener.cpp]
#include "listener.h"
Listener::Listener(QTcpSocket *socket, QObject *parent) :
QObject(parent),
_socket(socket)
{
// I guess this is where it goes wrong
connect(_socket, SIGNAL(readyRead()), this, SLOT(acceptData()), Qt::QueuedConnection);
}
void Listener::acceptData()
{
QByteArray data = _socket->readAll();
cout << data.constData();
}
The thing I do not get is that the error message claims that I try to connect some signal from QThread (and I clearly do not: see listener.cpp:8); 我没有得到的是错误消息声称我尝试连接来自QThread的某些信号(并且我显然不这样做:请参见listener.cpp:8)。 even stranger is that this only happens when the socket is created by the QTcpServer instance, not in the other case.
甚至更奇怪的是,这种情况仅在套接字由QTcpServer实例创建时才会发生,而在其他情况下则不会。 What am I missing?
我想念什么?
See my own answer. 看到我自己的答案。
I do not use an extra thread anymore (see comment). 我不再使用额外的线程(请参阅注释)。 The problem was deleting the QTcpServer instance in
Peer::acceptPeer()
, once a connection was established. 问题是一旦建立连接,就删除
Peer::acceptPeer()
的QTcpServer实例。 I thought that I could delete it because I only need that one socket QTcpServer::nextPendingConnection()
returns. 我以为可以删除它,因为我只需要返回一个套接字
QTcpServer::nextPendingConnection()
。 Apparently this is wrong, the socket is probably destroyed as well, leaving me with a rogue pointer (I think) crashing the program. 显然这是错误的,套接字也可能被破坏,使我留下了流氓指针(我认为)使程序崩溃。 Now I only call
_server->pauseAccepting();
现在我只调用
_server->pauseAccepting();
right after I get the socket, and all works fine. 在我获得插座后,一切正常。
Here is the change I've made: 这是我所做的更改:
void Peer::acceptPeer()
{
disconnect(this, SLOT(acceptPeer()));
if (_isHost)
{
_socket = _server->nextPendingConnection();
_server->pauseAccepting(); // no deletion
}
_listener = new Listener(_socket);
}
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