A web application is running on a server. This application needs to fetch data from some other PC(Clients), which are on a different network.

On the clients' pc there are WCF hosted in Windows Services using its own local Sql db. That's why Server wants to get data from clients and client also want to get data from server.

I have no control over the firewall, proxy, NAT on the client side PC. Mostly company Employee PCs have lots of network security e.g firewall block ICMP traffic and some port too, Router might be Disabled port-forwarding etc .

Put another way, I want to make something like duplex communication between Server and Client so that clients and server are able to share data among each other.

e.g data share (data-table,data-set,string etc ) between Server and Client.

Computer A (server PC) is using Web-Page (.Net).

Computer B (client PC) is using a Desktop Application (WCF hosted in windows services) C# ..

Computer C (Client PC) is using a Desktop Application (WCF hosted in windows services) C#

All Computers A and B AND C are on different network and using Windows. There is no LAN networking between server and client pcs.

On the client side I don't want any setting on Router or proxy or Firewall . On clients side there is no IIS. i don't want to allow remote access on clients PC too. There are more than 500 Client PCs.

What is best most secure and fast way to handle this situation?

I have studied dual HTTP binding , MSMQ , Xsocket , Socket.io, SignalR, Websocket, WebRTC but I have too many questions to choose one.

I need communication server to client and client to server, not client to client.