Re: How can I make the server to call back to client without being blocked by firewall.

From: jeff Lee (
Date: 09/30/02

From: "jeff Lee" <>
Date: Mon, 30 Sep 2002 01:52:04 GMT

Thanks Bernie.

You helped me cleared sth.

Our application will have thousands of clients, and any one of them can make
connection to any one of others via our server. Therefore, our server has
to somehow do a call back to tell the called client that somebody is trying
reach him. I am sure we will hit fire wall when our server tries to open a
to the client.

We don't want to slack the client's fire wall at all, so I am thinking
an always on TCP connections from the clients to our server may solve the
Anyway all the clients have to log in before they can make a call or be

Do you think this will work?

Also since UDP is connectionless protocol, it won't work for this, will it?



"Bernie M" <while_up_late@night> wrote in message
> "jeff Lee" <> wrote in message
> news:7Vil9.38097$wH.4116@sccrnsc01...
> > All,
> >
> >
> > We are developing a client server applications, and speculating that
> > the server may have the problems to make call backs
> > because of the firewall.
> >
> > Can anybody tell me what technics / protocol to use to solve the
> >
> > Regards,
> >
> > Jeff
> >
> When you say "call backs" do you mean the server will initiate a TCP
> back to the client?
> To "solve the problem" you should be speaking to the firewall
> As an application developer you should be able to provide the
> with specific information about what protocols, port numbers (perhaps even
> application specific url's etc.) that your application will need allowed
> through the firewall.
> The last thing you want to do is to get off-side with those that can help
> you and, besides, you don't want to do anything that puts the companies
> network at risk do you? Attempting to get around any restrictions may be
> (should be) a sackable offence.
> BernieM