# Re: Applet receiving multicast msg ?

Roland Schemers (Roland.Schemers@Eng)
Wed, 29 Apr 1998 23:41:11 -0800 (PDT)

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    From: Roland.Schemers@Eng (Roland Schemers)

    Message-Id: <199804300641.XAA02227@crypto.eng.sun.com>

    Subject: Re: Applet receiving multicast msg ?

    To: pledru@pluto.cs.uah.edu (Pascal Ledru)

    Date: Wed, 29 Apr 1998 23:41:11 -0800 (PDT)

    In-Reply-To: <3549218E.2DDD@cs.uah.edu> from "Pascal Ledru" at Apr 30, 98 08:12:46 pm

I have often wondered the same thing myself. Since multi-cast addresses
are just class D IP addresses I'm not sure why checkConnect/etc didn't
cut it. In 1.2 the default implementations of checkMulticast
in SecurityManager simply convert the IP address to a string and
call checkConnect. People are still free to implement their own
version of checkMulticast though.

Maybe in JDK 1.1.7 we should allow trusted-signed applets to do
multicasting. That seems like a reasonable fix. We are already
planning on allowing trusted applets to access the event queue
and delete files (that they are allowed to write to).

roland

>
> It seems that Applets cannot receive and send multicast messages.
>
> In the MulticastSocket class checkMulticast is called in joinGroup and in send.
>
> So an applet will not be able to receive a multicast msg even if the multicast
> msg is from the host where the applet is from.
>
> It seems to me that this is too restrictive.
> Why is it necessary to call checkMulticast in joinGroup and not only in send
> and receive? (where in receive it will check that the msg is coming from the
> host where the Applet is from with a call such as dp.getAddress().getHostName()
> )
>
> It seems to me that this preclude lot of applications where I don't see
> security problems.
>
> For example, if RMI one day support MulticastRemoteObject, the Applet stock
> notification example given by Sun could be implemented with
> MulticastRemoteobject
> which itself would probably use a MulticastSocket (only for receiving msg)
>
> Does anybody known why Applets cannot receive multicast msg?
>
> Thanks?
>
> Pascal Ledru
>

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