Re: Of Channels, Firewalls and Callbacks...

From: Sunny (sunnyask_at_icebergwireless.com)
Date: 03/29/04 

Date: Mon, 29 Mar 2004 10:54:13 -0600

Hi,
this is happening, becouse for the callbacks the server tries to open a
new connection to the client's listening port. As far as you are behind
a firewall with only port 80 open, server can not open the connection to
the client.
You may encounter a second problem as well. If your client is also NAT-
ed, the server can not reach it also.

Possible solution (if client is not NATed) - do not use HttpChannel(0)
at client side. Specify a hardcoded port. And open that port in the
server's firewall, so it can reach the client.

If the client is NAT-ed also, you have some options:

I saw that Allen Anderson has an article for solving dome firewall/NAT
problems with CAOs. I haven't tried it, but so far I haven't seen any
bad advise from him :). The link is:
http://www.glacialcomponents.com/ArticleDetail.aspx?articleID=CAOMN

Also, you can take a look at www.genuinechannels.com. They have their
custom channels (including HTTP) which are working very well in proxy
and/or firewall configurations. I'm using them.

Hope that helps
Sunny

In article <#mC76cZFEHA.684@tk2msftngp13.phx.gbl>, news@hyper-typer.com
says...
> Hi again all,
>
> I'm trying to understand the interplay between the channels and a firewall.
> Here's my setup, I have a client which has a http channel registered on say
> port 5150 to receive a callback. My server object is hosted in IIS. IIS is
> stting behind a NAT firewall with port 80 open and a mapping to the IIS
> I.P - I can reach the web.server with no problems using my browser over the
> Internet so I know that's ok. If my client and server reside on the same
> machine I have no problem getting a callback. However, if I use the remote
> IIS server described above I can call methods but don't recieve callbacks.
> Instead I get an error informing me that the underlying connection was
> closed after about 120 seconds. Given that there is no firewall operating
> on my client does anyone have any ideas what's going on - I have tried
> opening up a corresponding port on the server for the client http channel
> without success so any thoughts would be appreciated.
>
> Regards,
>
> Blue Frog
>
>
>

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