chat client might block in some organization with strong fireball ?? + some Ajax examples in rev

[Alex Tweedly]

Dan Shafer wrote:

>Presumably one could write a chat client that uses a generally open
>port (such as 80) for communication. But clearly both ends (and all
>users) would have to open whatever port is chosen.
>
>  
>
Even that will fall foul of many firewalls. It's common to close off 
port 80 to incoming connections, except to specified server machines, or 
to as specific server subnet (or range of IP addresses for the servers).

>On 1/18/06, MITTAL Pradeep Kumar <PradeepKumar.MITTAL at insead.edu> wrote:
>  
>
>>Hello,
>>
>>I saw an simple example of client server chat application in revolution.
>>It runs on some specific port number. So first of all on the server side
>>one has to open the port for all so that users outside can access the
>>chat server. Ok that can be done, not a big deal.
>>
>>Will not this socket connection block in some organization who has
>>strong fireball.?? On should that same port also be opened by the client
>>organzation? I guess yes. ( even org has to open the port for yahoo and
>>msn messangers )
>>
>>    
>>
Yes. Your best chance of avoiding firewall problems is to use a 
well-known port, have each client open a connection on that port to the 
server(s). This will work on most corporate networks (though it does 
require that you have servers in a location where they can accept 
incoming connections on such a port).

Some firewalls will not simply open the port, but actually check within  
the packet for application protocol (this is fairly extreme). To get 
around that, you can do everything as a client initiated http request 
with either polling or very long time-outs for "async" output (though a 
site using extreme firewalling plus application level gateways/proxies 
could block even that).

>>So can not we have any chat application in revolution which has no
>>fireball issues?? Is there any mechansim so that we can have two way
>>connection in rev ( push and pull)??
>>
>>Do you have any examples or idea which can demonstrate ajax mechanism in
>>rev?
>>    
>>
A corporate site which has tight firewalling is also likely to have 
strict constraints on users installing their own applications - so the 
scope for using a Rev-based client app (i.e. not within the browser) is 
probably limited.


-- 
Alex Tweedly       http://www.tweedly.net



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