Setting up an FTP server on Windows Server 2008/2012 should be straightforward, but many admins hit this exact roadblock. The server responds perfectly to local connections:

C:\>ftp localhost
Connected to WebHead1
220 Microsoft FTP Service

Yet remote connections mysteriously time out:

~>ftp x.x.x.x
ftp: Can't connect to x.x.x.x': Operation timed out
ftp: Can't connect to x.x.x.x'

While you've enabled "FTP Server" in Windows Firewall, IIS FTP requires specific rules:

netsh advfirewall firewall add rule name="FTP Service" action=allow protocol=TCP dir=in localport=21
netsh advfirewall firewall add rule name="FTP Passive" action=allow protocol=TCP dir=in localport=49152-65535

For passive FTP (the default in IIS), you must also configure port ranges in IIS Manager:

1. Open IIS Manager > FTP Firewall Support
2. Set "Data Channel Port Range" to 49152-65535
3. Enter your external IP in "External IP Address"

Three often-overlooked network issues:

# Verify basic connectivity first:
Test-NetConnection x.x.x.x -Port 21

If this fails, check:

• NAT configuration on routers (port forwarding 21 AND passive range)
• ISP blocking port 21 (common in residential networks)
• Corporate firewalls intercepting FTP traffic

Add these diagnostic commands to your toolkit:

# Check if FTP service is actually listening:
netstat -ano | findstr :21

# Verify IIS authentication settings:
Get-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' 
  -filter "system.ftpServer/security/authentication/*" 
  -name "enabled" | Format-Table -AutoSize

Modern networks often break passive FTP. Implement this PowerShell fix:

# Set passive mode response to external IP
Add-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' 
  -filter "system.ftpServer/firewallSupport" 
  -name "externalIp4Address" -value "YOUR_EXTERNAL_IP"

# Configure data channel ports
Set-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST' 
  -filter "system.ftpServer/firewallSupport" 
  -name "dataChannelPortRange" -value "50000-50100"

Use Wireshark with this capture filter:

tcp port 21 or tcp portrange 49152-65535

Look for:

• SYN packets reaching your server
• SYN-ACK responses from IIS
• ACK completion (or lack thereof)

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This is one of those frustrating situations where your IIS FTP server appears perfectly configured - it accepts local connections via ftp localhost or 127.0.0.1, but times out completely when attempting remote access. Let's break this down systematically.

Even though you've checked "FTP Server" in Windows Firewall, there's more to it:

# Check specific FTP firewall rules with PowerShell
Get-NetFirewallRule -DisplayName "FTP*" | Select-Object DisplayName,Enabled,Profile,Direction,Action

# Example output should show both inbound rules enabled:
# DisplayName       : FTP Server (FTP Traffic-In)
# Enabled           : True
# Profile           : Any
# Direction         : Inbound
# Action            : Allow

If these aren't enabled, create them manually:

New-NetFirewallRule -DisplayName "FTP Server (Port 21)" -Direction Inbound -Protocol TCP -LocalPort 21 -Action Allow
New-NetFirewallRule -DisplayName "FTP Passive (Port Range 50000-50100)" -Direction Inbound -Protocol TCP -LocalPort 50000-50100 -Action Allow

Before blaming IIS, verify basic connectivity:

# From remote machine test basic connectivity:
telnet x.x.x.x 21
# or with PowerShell:
Test-NetConnection x.x.x.x -Port 21

If these fail, the issue is network-related, not FTP-specific. Check:

• NAT configurations if behind a router
• ISP blocking port 21 (common in residential networks)
• Corporate firewall restrictions

The "All Unassigned" IP binding can sometimes cause issues. Try explicitly binding:

# In IIS Manager:
1. Select FTP Site -> Bindings
2. Add explicit binding for server's public IP
3. Restart FTP service

For advanced scenarios, check the IIS configuration file:

# Location:
%SystemDrive%\\inetpub\\temp\\appPools\\YourFTPSite\\config\\applicationHost.config

# Look for <site> node with your FTP configuration
# Verify bindings and physical path

Many remote connection failures stem from passive FTP misconfiguration. In IIS:

1. FTP Firewall Support settings must match your public IP
2. Define a passive port range (e.g., 50000-50100)
3. Ensure firewall allows this range

For complex NAT scenarios, you might need:

# In IIS 7.0+ applicationHost.config:
<ftpServer>
  <firewallSupport>
    <externalIpAddress>your.public.ip</externalIpAddress>
    <dataChannelPortRange min="50000" max="50100" />
  </firewallSupport>
</ftpServer>

Enable detailed logging (IIS Manager -> FTP Logging) and examine:

# Default log location:
%SystemDrive%\\inetpub\\logs\\LogFiles\\FTPSVC1\\

# Filter for failed attempts:
Select-String -Path "*.log" -Pattern "FAILED"

For real-time monitoring, use:

# PowerShell command to watch logs:
Get-Content -Path "C:\\inetpub\\logs\\LogFiles\\FTPSVC1\\*.log" -Wait

When traditional methods fail, try these advanced techniques:

# 1. Use PortQry to test FTP service response:
portqry.exe -n x.x.x.x -e 21 -p TCP

# 2. Check if IIS actually received the request:
netsh http show servicestate view=requestq

# 3. Verify the FTP service is listening:
netstat -ano | findstr ":21"

As a last resort, completely reset IIS and FTP components:

# Remove and reinstall FTP service:
dism /online /disable-feature /featurename:IIS-FTPServer
dism /online /enable-feature /featurename:IIS-FTPServer

# Reset IIS configuration:
%windir%\\system32\\inetsrv\\appcmd list site /xml > backup.xml
iisreset /stop
del /q /s %windir%\\system32\\inetsrv\\config\\applicationHost.config
iisreset /start

Remember to restore your configuration from backup.xml after verification.

• Verified physical network connectivity
• Confirmed port 21 isn't blocked by ISP
• Checked both Windows Firewall and any third-party firewalls
• Validated IIS bindings and FTP site permissions
• Reviewed detailed FTP logs for connection attempts
• Tested with multiple FTP clients (FileZilla, WinSCP, command-line)