The edited part of @JonB is important, you have to read the data.

@karthik23 said: where should i insert this code exactly? where you need it :) I mean u asked the question because you want to achieve something. Since it's still not very clear what you want as the final result, i can't help you. For testing you can add it in the line where your qDebug() calls is.

@mrjj Thank you a lot, it works!!!

First, you need to have public IP on your server PC, that is: a) you must have only one router (not two or more cascaded in your home), and b) you must use UPnP to open the ports you want to listen on. Unfortunately, for whatever reason, Qt never bothered to at least port a UPnP library (e.g. miniupnp) to Qt. Second, you need to know, from the outside, sour server's IP: for this you need a "known server" with a known static IP where you should publish your server PC's IP each time the server starts, or use something like dyndns. Finally, even with the setup above, you can only use this solution if your server PC does not connect via a mobile network, because in that case you can't open any UPnP ports on your provider. (see http://stackoverflow.com/questions/13996361/getting-around-nat-for-p2p-app-if-i-have-all-ip-info/14202854#14202854 )

@ealione said: How can I get all open connections on my TCP server? You need to do this in the code?? In that case you have to store the list on connections in some containers (QVector, QMap, ...)

Hi Arthur, Very interesting link. Actually some of his other projects look quite interesting too, albeit being in german.