Instant Server-Client Communication, C#?

I have been doing research for a few months now on the possibility of client-server communication. I have experimented with many methods such as WebORB and FluorineFX, which are both servers designed to deal with client/server authentication.

WebORB only runs on Windows for their .NET version as far as I can tell, and I would much rather use an open source system. I have tried using FluorineFX, but I think their must be a simpler way for me to build my own simple system from the ground up.

I have been using Dropbox for a while now, and I like the way that the client-server communication is in开发者_开发知识库stant. As far as I can tell (from some Google searches) the client doesn't open a port of its own, and just communicates with the Dropbox server through port 80. An example of its instant communication is where you may delete a file on Dropbox on their website, and instantly the server communicates with the client telling it what has happened. I don't know how this instant communication is possible without opening a port.

I can create a system that uses fetching from the client, asking the server every 10 seconds or so to see if there are any updates, but I would like a method to be able to push the information from the server to the client.

My server runs Linux so I don't think I can use WCF, and ideally I am looking for a way to make PHP and C# communicate with each other.

I would love to hear any advice that anyone has and how they deal with the problem. Cheers.

You CAN use WCF to communicate with any platform. Just make sure you're using an endpoint which your target machine support: http://msdn.microsoft.com/en-us/library/ms733107.aspx

Have you tried the good old .NET Remoting which runs perfectly with Mono?

You can choose between a TcpChannel (for performance) and a HttpChannel (to pass proxy/firewall easily).

For push notifications, you can open a connection to your server and wait for an answer indefinitely.