How can i use TCPIP to transfer data between 2 computer which are not in the same local network

Dear all,

I am fresh to Matlab TCPIP. I am struggling to transfer data between 2 Matlab machines using TCPIP. I successfully operated in local network however i failed when i tried to communicate through internet to an external network (I specified the server external IP to the client). Does anyone know how can i communicate between 2 computer which connected to internet but are not in the same local network? So much appreciate!

Thanks