I was just testing and trying to know more about virtual box. I came across the internal network thing and to test it out I tried using two virtual linux systems. All the settings are correct but both the OS are showing same ip. How can I check whether they are connected or not? How can I sent files between the two?
I guess your interfaces are configured to use NAT, in such case, they are not connected to the same network and are unreachable to each other (outside port forwarding).
You should add a new interface and use one of the other networking modes (bridge, internal network, ...) for the virtual NICs to see each other.
If you want to stay in NAT, one simple way to "send" files from/to your VMs would be to use a shared folder.
If you are already using the same internal network, the issue is both VMs are showing the same IP and then can't communicate at the IP level.
Either set the IP address of the second VM to something else in the same subnet or enable the dhcpserver on the virtualbox size and configure the VMs to get their IP address from dhcp instead of using fixed addresses.
That way you won't have the same IP address on each server and then can have them communicate through the network.
Check they see each other with
To transfer files between the VMs, you can use ftp, scp, nfs, samba, ...