How do I make a chat app over internet

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C++

PHP

Internet

Chat

I have a problem of connection between two application ( with c++ builder ), the apps are working good in a local network, but aren't work in the internet, `cause both of the client and the server are in deferent routers, and each one have an internal & external IP, I think u understood me.

So, I searched in forums and I found two solution:
1 - NAT: I think you know it, it didn't help me, I got two problems:
N°1: is when you lunch your app in a cyber cafe for example, you can`t access to the modem to setup the NAT.
N°2: i`m not sure but I read that it doesn't work if the both of the client and the server are using the NAT.
2 - A web server, that who makes the relation between the two apps, without a NAT setup.:-( but it need a web site, I have try it with a free web site from http://WWW.Hostinger.com , and i wrote a php code, but without result, I failed.

Can any one help me please, show me where I failed, or give me an other solution.
& thanks.