how to handle client Fire Wall , router in duplex communication ?

I want to make simple demo in win form like "hello" send from client and server response back to that client. client <==> Server. duplex communication .

client ,server both are on different network .

I had try to use socket ,web socket. Signal R ,X socket , socket .but i could not resolve the issue of Firewall on client side. of course on localhost everything work fine LOL.

i mean if client is behind firewall and firewall of client block ICMP traffic then connection fail with server. client can't initiate connection with server .

client <==> firewall <==> proxy <==> Router <========> (Internet) <===> server

ICMP traffic block mean client can't ping Google,yahoo,or any thing. but can access them.

Client Router can disabled port forwarding trick also . as you know these days different type of router.

i also did try to use port 80 but still fail . i wondering how skype working lol. Any way i don't want to any setting on client router or firewall etc..

note: I should use Window Form application . not Web .
Please give me good trick to use which should faster ,secure and easy to implement.


i'm looking forward your response . Thanks Advance .