Comments by TheQult (Top 2 by date)

99% it's not a problem with the code but with networking.
in lan they are both on the same network and they see each other.
But when your server it's on the internet and you client it's in your lan, wich is probably a NAT, the client can see the server but the server can not see the client.

Simplest solution: the client open the connection and keep it opened, the server use the connection opened by the client