Question : Port and Chat Client

I just have some questions about ports and chat clients.

I am aware that if someone from the outside tries to talk to a port on my machine I need to make sure it routes to the right machine and port in my router, the firewall lets it through etc..

But what I do not know is what happens when the communication is initiated from the other side, for example;
I have created a chat server and chat client in Java, the chat server listens on port 8010, so the client tries to communicate to port 8010 on my server, I am thinking that the client will not have to do anything and is just able to always reach my port 8010, am I correct?

Are there any ports that I should be using?

Answer : Port and Chat Client

sorry, better description should be this:
client port is dynamic allocated when every session(a connection to server) start, and be hold on the whole specific session lifetime.
In UDP diagram mode, client just send data, that's ok.
In TCP stream mode, client first connect server, server can deside accept connection or not. if server accept connection, server send back a package to notify client connection is build. then client and server can send data to opposite end.