You have a network like this
Internet
|
Router
|
/ \
/ \
PC1 PC2
Local network has 3 interfaces, PC1, PC2 and internal Router port. This interfaces has private IP addresses like 192.168.1.1.
External network (internet) has public IP address. When you try to connect over internet, with public IP address you receive an answer from your router, not from your PC. Try to make a port forwarding for your pc IP address via your router configuration page.