The red and blue, Red5 and BlazeDS are available for push mechanisms similar to what Comet is trying to accomplish with sockets essentially that use the AMF format and AMF3 format with Flash/Flex that is extremely optimized for size and thus network traffic is less bulky.
Welcome to BlazeDS! BlazeDS is the server-based Java remoting and web messaging technology that enables developers to easily connect to back-end distributed data and push data in real-time to Adobe® Flex™ and Adobe AIR™ applications for more responsive rich Internet application (RIA) experiences.
The evolution to more engaging RIAs has created the need for better data connectivity options. Remoting simplifies the reuse of existing server logic automatically marshalling calls between the Flash client and the Java methods on the server. In addition, the use of a AMF binary data transfer format increases performance, allowing applications to load data up to 10 times faster than with text-based formats such as XML or SOAP.
Previously available only as part of Adobe LiveCycle® Data Services ES, Adobe is contributing the proven BlazeDS technologies to the community under the LGPL v3. BlazeDS gives the rapidly growing Adobe developer community free access to the powerful remoting and messaging technologies developed by Adobe.
The odd thing about all this is both Red5 and BlazeDS are Java based. The AMF integration with Java is pretty solid with two major push capable servers using that (again with sockets behind the scenes but highly optmized with AMF/AMF3 and in multiuser case with remote shared objects – red5).
Push mechanisms are needed more and more and having this capabilty right into flash with AMF format remoting data proves to be very easy to integrate and if the backend is java then a pretty robust back end as well.
I use PyAMF for Python and Flourine for .NET as well as the usual AMFPHP but the need to push and have more optimization than a basic object socket connection might be in order.