Threading / Concurrency Issue - D

TcpSocket Server;
Thread ReceiveThread;
Connection[int] Connections;

void Start(string IPAddress, ushort Port)
{
    Server = new TcpSocket();
    Server.bind(new InternetAddress(IPAddress, Port));
    Server.listen(500);

    ReceiveThread = new Thread(&HandleReceive);
    ReceiveThread.start();

    HandleAccept();
}

void HandleAccept()
{
    while (true)
    {
        Socket connectedSocket = Server.accept();

        Connection conn = new Connection;
        conn.socket = connectedSocket;

        synchronized
        {
            conn.key = GetKey();
            Connections[conn.key] = conn;
        }

        // it gets here and the connection is added to the collection ...

        Thread.sleep(dur!("msecs")( 1 ));
    }
}

void HandleReceive()
{
    while (true)
    {
        synchronized
        {
            // never loops ...
            foreach (Connection conn; Connections.values)
            {
                // doesn't even get here ...
                writeln("Handling ...");
                if (conn.Handled)
                    continue;
                conn.Handled = true;

                writeln("Receiving ...");

                ubyte[] recBuffer = new ubyte[1024];
                int ReceiveSize = conn.socket.receive(recBuffer, SocketFlags.NONE);

                writeln("Received ...");

                conn.socket.send("Hello World!");

                writeln("Send ...");

                conn.socket.shutdown(SocketShutdown.BOTH);
                conn.socket.close();

                Connections.remove(conn.key);

                writeln("Removed ...");
            }
        }
        Thread.sleep(dur!("msecs")( 1 ));
    }
}