Return the server port in listen()

It allows knowing the server port in case the user chooses to use a
random port. In the previous implementation listen() was returning a
boolean value making it impossible to know the port number.

Change-Id: I73384188b3b2eb57816eb6c6c9a7ac1a511b7456
Reviewed-by: Mikhail Svetkin <mikhail.svetkin@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/httpserver/qabstracthttpserver.cpp

@@ -156,17 +156,19 @@ QAbstractHttpServer::QAbstractHttpServer(QAbstractHttpServerPrivate &dd, QObject
 /*!
     Tries to bind a \c QTcpServer to \a address and \a port.
 
-    Returns \c true upon success, false otherwise.
+    Returns the server port upon success, -1 otherwise.
 */
-bool QAbstractHttpServer::listen(const QHostAddress &address, quint16 port)
+int QAbstractHttpServer::listen(const QHostAddress &address, quint16 port)
 {
     auto tcpServer = new QTcpServer(this);
     const auto listening = tcpServer->listen(address, port);
-    if (listening)
+    if (listening) {
         bind(tcpServer);
-    else
+        return tcpServer->serverPort();
+    } else {
         delete tcpServer;
-    return listening;
+        return -1;
+    }
 }
 
 /*!

src/httpserver/qabstracthttpserver.h

@@ -61,7 +61,7 @@ class Q_HTTPSERVER_EXPORT QAbstractHttpServer : public QObject
 public:
     QAbstractHttpServer(QObject *parent = nullptr);
 
-    bool listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0);
+    int listen(const QHostAddress &address = QHostAddress::Any, quint16 port = 0);
 
     void bind(QTcpServer *server = nullptr);
     QVector<QTcpServer *> servers() const;