问题描述：

//tcp_client.cpp:19:23: Static_cast from 'SocketError (QAbstractSocket::*)() const' to 'void (QTcpSocket::*)
//(QAbstractSocket::SocketError)' is not allowed

原因分析：
QtNetwork中的错误信号error换成了errorOccurred
 

QT5.0

connect(tcpClient,static_cast<void (QTcpSocket::*)(QAbstractSocket::SocketError)>(&QTcpSocket::error),this,[=]{
qDebug()<<"tcp error:"+tcpClient->errorString();
});

QT6.0

connect(tcpClient,static_cast<void (QTcpSocket::*)(QAbstractSocket::SocketError)>(&QTcpSocket::errorOccurred),this,[=]{
qDebug()<<"tcp error:"+tcpClient->errorString();
});