Passing a QLocalSocket* to a method expecting a QIODevice* - qt

Question

Perhaps I'm being over-ambitious, but I'm trying to write a server program which can accept connections over both QLocalSockets and QTcpSockets. The concept is to have a 'nexus' object with both a QLocalServer and QTcpServer listening for new connections:
Nexus::Nexus(QObject *parent)
: QObject(parent)
{
// Establish a QLocalServer to deal with local connection requests:
localServer = new QLocalServer;
connect(localServer, SIGNAL(newConnection()),
this, SLOT(newLocalConnection()));
localServer -> listen("CalculationServer");
// Establish a UDP socket to deal with discovery requests:
udpServer = new QUdpSocket(this);
udpServer -> bind(QHostAddress::Any, SERVER_DISCOVERY_PORT);
connect(udpServer, SIGNAL(readyRead()),
this, SLOT(beDiscovered()));
// Establish a QTcpServer to deal with remote connection requests:
tcpServer = new QTcpServer;
connect(tcpServer, SIGNAL(newConnection()),
this, SLOT(newTcpConnection()));
tcpServer -> listen(QHostAddress::Any, SERVER_COMMAND_PORT);
}
... and then separate slots which establish a server object, whose constructor takes a pointer to a QIODevice. In theory, this ought to work because both QLocalSocket and QTcpSocket inherit QIODevice. Here is the newLocalConnection slot, for example:
void Nexus::newLocalConnection()
{
// Create a new CalculationServer connected to the newly-created local socket:
serverList.append(new CalculationServer(localServer -> nextPendingConnection()));
// We don't allow more than one local connection, so stop listening on the server:
localServer -> close();
}
The problem is that this won't compile, giving an error:
error C2664:
'CalculationServer::CalculationServer(QIODevice
*,QObject *)' : cannot convert parameter 1 from 'QLocalSocket *' to
'QIODevice *' 1> Types pointed
to are unrelated; conversion requires
reinterpret_cast, C-style cast or
function-style cast
Now the types pointed to are clearly not unrelated, and elsewhere in my code I have no problems at all with actions like:
QLocalSocket *socket = new QLocalSocket;
QIODevice *server = new QIODevice;
server = socket;
... so can anyone tell me why the compiler has a problem with this? Is there a way that I can make the constructor accept the QLocalServer*? I suppose there is the nuclear option of getting the constructor to take a void pointer plus an extra variable to tell it what it's being sent, so it can then recast the void pointer to either a QLocalSocket or QTcpSocket, but I feel uncomfortable resorting to reinterpret_cast on what looks like it ought to be a straightforward bit of C++ polymorphism.
Regards,
Stephen.

Answer 1

The most likely reason is that you have forgotten to #include <QLocalSocket> in the source file where the error occurs.