Multi thread server can not read messages from clients in Qt - c++

Question

Trying to implement a multi thread server in Qt, just consider this:
in SocketThread class:
SocketThread::SocketThread(qintptr descriptor, QObject *parent)
: QThread(parent), socketDescriptor(descriptor)
{
socket = new QTcpSocket();
socket->setSocketDescriptor(socketDescriptor);
socket->moveToThread(this);
connect(socket, &QTcpSocket::readyRead, [this]() { qDebug() << socket->readAll(); }); //trying to read messages from clients
}
in Connection class: creating thread in incomingConnection()
void Connection::incomingConnection(qintptr socketDescriptor)
{
SocketThread *socketThread = new SocketThread(socketDescriptor);
socketThread->start();
connect(socketThread, &SocketThread::started, [&]() { socketThread->socket->write("Hello!"); }); //write a message to client when thread is created
}
Strange thing is, if I add this line:
connect(socketThread, &SocketThread::started, & { socketThread->socket->write("Hello!"); }); //write a message to client when thread is created
Then the socket will not read message from client. If I remove that line, the socket will read message from client.
I want the server to send message to client when a thread is created and to read message from client as well. How can do solve the problem?
Edit:
SocketThread header file:
class SocketThread : public QThread
{
Q_OBJECT
public:
SocketThread(qintptr descriptor, QObject *parent = 0);
~SocketThread();
QTcpSocket *socket;
qintptr socketDescriptor;
};
in the Connection constructor:
Connection::Connection(QObject *parent) : QTcpServer(parent)
{
this->listen(QHostAddress::Any, 6666);
}
And creating a connection object in the main.cpp file. That's really like all the code.