Having problem reaching client which don't have static ip address

i am making a messenger over internet.

it has a server which listens to clients but when it try to send the reply to any request to client it shows the error of client not found. however my clients are connecting to that server because it has a static ip address and live server.

having problem reaching client becaus开发者_开发技巧e they can be behind any firewall or network and dont have static ip addresses. so how can i reach to my client?? any Suggestions..

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Make sure that the firewall isn't causing any problems and also checkout NoIp(http://www.no-ip.com/), it allows any computer to effectively have a static ip. Just sign up then click on "Add Host". Call the host whatever you want then, on your client program set the ip as the name of the host. As long as the no-ip duc program (a very small, portable program you need to download) is running, it should work fine :) Hope it works, ell.