FileCOPA FTP Server allows you to use non-standard port numbers, even if you are behind a router. Reasons for this may be:
| • | You wish to make the presence of your FTP server less obvious to hackers. |
| • | You wish to run more than one FTP server on the same machine, or on different machines on your network, all accessible from outside. |
As explained on this page, most routers will automatically handle connections via the standard FTP port (21), appropriately translating ports and IP Addresses. But they may not handle the use of non-standard ports in the same way.
Let us assume that you wish to configure FileCOPA FTP Server as in the image above.
You will use port 7478 as the listening port for your server - ensure that your router/firewall forwards/allows all connections to this port to the machine running FileCOPA FTP Server
You will use ports 7480 to 7490 for incoming connections via Passive FTP - again ensure that your router/firewall forwards/allows all connections to these ports to the machine running FileCOPA FTP Server.
As explained on the page about The Principles of FTP, FileCOPA FTP Server would normally, when requested to initiate a Passive connection for data transfer, send the IP Address of the machine on which it is running, which may well be a private, internal address, not routable from the internet. Using this configuration however, FileCOPA can be forced to send a specified IP address or machine name (it will automatically do a DNS lookup if you have entered a name). This should be the external address of your network, and the client will then be able to connect.
If you have more than one network card in your server machine, is it possible to limit the IP Addresses via which FileCOPA is accessible.
For example you may wish it only to be accessible from within your network, not from the internet. For this you would need two network cards in the machine, one providing access to the Local Area Network, and another providing access from the internet only.
NOTE that if you use a router with Port Forwarding using NAT (Network Address Translation), incoming connections from the internet may well be forwarded to the LOCAL address, and if you bind FileCOPA to this local address, you are effectively making it available to connections from the internet.
The image above shows a machine with only one network card (IP Address 192.168.254.7). The IP Address 127.0.0.1 is the Local Loopback or Localhost address - access from this machine only. A configuration like the above is useful if testing FileCOPA, so that it is only accessible from the FileCOPA server machine, not to any others on your network, or from the internet.