You have downloaded and installed Open Source Filezilla FTP Server on Windows Server 2008 R2.  You have configured it in the passive mode to connect only on TCP Port 21 by entering in the port range From 21 To 21, which is the standard FTP port.  You are behind the NAT on your Router so, when configuring Filezilla after installation, you have entered the static public IP address of your router on which port forwarding is configured to forward from port 21 on the public IP to port 21 on your server’s bind local IP.

You fire-up your FTP client and try connecting to the Filezilla server to no avail.  You already setup a user and password and default directory on the Filezilla server.  However, it might not be connecting because your Windows Firewall is likely blocking ftp reception on port 21 at the server.

Let’s use the Microsoft Management Control (MMC) Snap-in to open TCP port 21 inbound.

Click “START” button, and point to “Programs,” “Administrative Tools,” and select “Windows Firewall with Advanced Security.”

In general, Windows firewall is enabled and, by default, inbound connection that do not match a firewall rule are blocked.  By default, all outbound connections that do not match a firewall rule or allowed (not blocked).  So, we may need to add and inbound rule.

Right-click “Inbound Rules” and left-click “add New Rule,” or select “Inbound Rules” on the left and click “New Rule” under the actions section on the right.

Rule TYPE:  Select “Port” and click Next.

Rule PROTOCOL: Select “TCP,” Select “Specific local ports” and enter “21” and click Next.

In the “ACTION” section, select “Allow the Connection” and click Next.

In the “PROFILE” section, make sure that all 3 check boxes are checked for Local, Domain, and Public.

In the ‘NAME” section, type something like “TCP port 21 for FTP service.”  In the DESCRIPTION  text box, you may add whatever explanation you wish, such as “Custom Inbound Firewall Rule to Allow FTP communication on standard TCP port 21 — MyRule.”

Click Finish.

Test your connection from FTP client to Filezilla server now.