PyQt子类QTcpServer和QTcpSocket

Question

我正在尝试使用PyQt5.QtNetwork.QTcpSocket和PyQt5.QtNetwork.QTcpServer作为基础来实现自定义的TCP和服务器。文档声明必须重写QTcpServer.incomingConnection才能返回自定义套接字对象。这在原则上似乎很好，但我总是在一些奇怪的行为上犹豫不决。在调用QTcpServer.nextPendingConnection时，该方法似乎确实返回了预期的MyNewSocket实例，但是，当一个人访问新套接字的任何属性或方法时，解释器首先返回said属性/方法，然后再通知您，到目前为止我还没有找到合理的解释的AttributeError: 'NoneType' object has no attribute 'anyAttribute'。这里是一个MWE，它显示了这种行为。我使用的是PyQt5版本5.15。

tcpmodule.py

from PyQt5.QtNetwork import QTcpSockert, QTcpServer

class MyNewSocket(QTcpSocket):
    """do some additional stuff to the
       original QTcpSocket stuff"""
    pass

class MyNewServer(QTcpServer):
    def incomingConnection(self, handle):
        """Returns a MyNewSocket instance instead of
           original QTcpSocket instance"""
        socket = MyNewSocket(self)
        socket.setSocketDescriptor(handle)
        self.addPendingConnection(socket)
        self.newConnection.emit()

server.py

from tcpmodule import MyNewServer
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtNetwork import QHostAddress

app = QApplication([])
win = QMainWindow()
server = MyNewServer(win)
server.listen(QHostAddress.SpecialAddress.LocalHost, 9999)

def newConnection():
    socket = server.nextPendingConnection()
    print("Acces any Attribute ", socket.connected)
    print("Socket is ", socket, " Socket Type is", type(socket))

server.newConnection.connect(newConnection)

win.show()
app.exec()

client.py

#!/usr/bin/env python3
from tcpmodule import MyNewSocket
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtNetwork import QHostAddress

app = QApplication([])
win = QMainWindow()

socket = MyNewSocket(win)
socket.connectToHost(QHostAddress.SpecialAddress.LocalHost, 9999)

def connected():
    socket.write(b"Hello, World!")

socket.connected.connect(connected)

win.show()
app.exec()

在运行server.py和后续的client.py连接之后，我得到以下输出

Acces any Attribute  <bound PYQT_SIGNAL connected of MyNewSocket object at 0x7f4be28597e0>                                                                                        
Socket is  <tcpmodule.MyNewSocket object at 0x7f4be28597e0>  Socket Type is <class 'tcpmodule.MyNewSocket'>                                                                     
Traceback (most recent call last):                                                       
  File "./server.py", line 13, in newConnection        
    print("Acces any Attribute ", socket.connected)                                      
AttributeError: 'NoneType' object has no attribute 'connected' 

有人能告诉我发生了什么事吗？！

Answer 1

根据文档，incomingConnection()似乎发出了newConnection()信号，但实际上没有。

通过查看资料来源，我们看到它只是创建了套接字，设置了它的描述符并将其附加到挂起的连接中：

void QTcpServer::incomingConnection(qintptr socketDescriptor)
{
#if defined (QTCPSERVER_DEBUG)
    qDebug("QTcpServer::incomingConnection(%i)", socketDescriptor);
#endif

    QTcpSocket *socket = new QTcpSocket(this);
    socket->setSocketDescriptor(socketDescriptor);
    addPendingConnection(socket);
}

实际上，信号只由私有函数readNotification()发出，该函数调用incomingConnection()并最终发出信号。

因此，您不必自己发出它，因为在第二次调用nextPendingConnection()时，您将得到一个nullptr (None)，因为之前的调用已经读取了套接字，并且没有更多可用的连接。