Server Pushed Messaging Over HTTP

[raghuposan]

Hey guys,



I have a question on Flex messaging. I am new to Flex data
services. Can somebody let me know if you guys have encountered the
same?



We wanted to use the Flex Messaging for showing real time
alerts in our application. We want to use Push mechanism and the
message channel that supports this is RTMP protocol. RTMP uses the
port number other than HTTP port number. The problem is our
application is behind the firewall and we have security retrictions
on opening a new port for RTMP.



Is there any way that we can use RTMP over HTTP. I have seen
an article saying that Flex channels are designed to be extensible,
such that independent software vendors may craft their own channel
implementations and integrate them into Flex Data Services. Is it
possible to have our own PUSH implementation that can run over
HTTP. Please let me know if anybody has used such implementation.
OR if we have any solution that we can use PUSH messaging that uses
HTTP.



I appreciate your time and help.



Best Regards,



Raghu

[Former Community Member]

Have you tried using amf-polling or http-polling channels?



HTH

Kumaran

[raghuposan]

Hi,



Thanks for the response. We tried amf-polling and executed
successfully. The problem with polling is even if the user does not
do any operations and as the polling process makes a continuous
request to the server the application will not timeout as mentioned
in the siteminder policy server.



To overcome this we want to use the flex messaging PUSH
mechanism and now we have the restriction of RTMP protocol used by
Push mechanism and RTMP uses Non http port number.



Best Regards,



Raghu

[Former Community Member]

raghuposan, in FDS 2.5 which is now called Livecycle Data
Services 2.5 (and it's currently in beta mode on Adobe Labs),
there's a new feature called HTTP push. It's not server push per
say but it acts like one. The way it works is that when a client
polls the server (using amf-polling or http-polling), if there are
no messages for the client, the poll thread will wait on the server
until a new message arrives. When the new message arrives, the poll
thread wakes up and client gets the message. This can be an
alternative to RTMP in your environment. All you need to do is to
setup a few parameter on HTTPChannel and AMFChannel definitions as
explained below:



<!-- Optional. Default is 0. This parameter specifies the
number

of milliseconds the server poll response thread will wait

for new messages to arrive when the server has no messages

for the client at the time of poll request handling. 0 means


that server does not wait for new messages for the client

and returns an empty acknowledgment as usual. -1 means that

server waits indefinitely until new messages arrive for the

client before responding the client poll request.

-->

<wait-interval-millis>0</wait-interval-millis>

<!-- Optional. Default is 0. This parameter specifies the
maximum

number of server poll response threads that can be in wait

state. When this limit is reached, the subsequent poll
requests

will be treated as having zero wait-interval-millis.

-->


<max-waiting-poll-requests>0</max-waiting-poll-requests>



So if you want to use HTTP push instead of RTMP push, you
would set poll-interval-millis parameter to zero (which means poll
as much as you can), then set wait-interval-millis to -1 (which
means wait on the server forever) and set max-waiting-poll-request
to something non-zero. That way, client will poll, if there's no
message for it on the server, it'll wait forever until a message
arrives and as soon as message arrives, client will get the message
and poll again. So there are no wasted polls.



Let me know if you need further info.