SFTP Connection Troubleshooting Guide

1. Basic Checks (All Platforms)

1.1 Verify Your Credentials

Double-check each field in FileZilla exactly as provided:

Field	Value	Common Mistakes
Host	tngsftp.blob.core.windows.net	Extra spaces, missing .net
Port	22	Using 21 (FTP) instead of 22 (SFTP)
Protocol	SFTP - SSH File Transfer Protocol	Selecting FTP or FTPS instead
Username	tngsftp.<your_sftp_user>	Omitting the tngsftp. prefix
Password	<your_password>	Trailing spaces from copy-paste

[[info=Tip]]Copy-paste carefully. When pasting credentials, make sure no leading or trailing whitespace is included. In FileZilla, type the password manually if copy-paste does not work.[[info]]

1.2 Confirm FileZilla Settings

Open FileZilla and navigate to File > Site Manager, then verify:

1. Protocol is set to SFTP - SSH File Transfer Protocol (not FTP or FTPS).
2. Logon Type is set to Normal (not Anonymous or Interactive).
3. Host field contains only the server address with no sftp:// prefix.
4. Transfer Settings tab: Transfer mode is set to Passive (this should be the default).

1.3 Try from a Different Computer or Network

To isolate whether the issue is with your machine or your network:

• Attempt the connection from a different computer on the same network.
• Attempt the connection from a different network (e.g. mobile hotspot, home Wi-Fi vs. office).

1.4 Check VPN and Proxy

If you are connected to a VPN:

• Try disconnecting the VPN and connecting directly.
• If a VPN is required by your organization, ask your network administrator to allow outbound traffic to tngsftp.blob.core.windows.net on port 22.
• If you use an HTTP proxy, note that SFTP (port 22) typically cannot traverse HTTP proxies. Speak with your IT team about a SOCKS proxy or a direct route exception.

1.5 Verify Azure / Microsoft Service Availability

Confirm that Azure Blob Storage services are operational in your region:

1. Visit the Azure Status page: https://status.azure.com
2. Check for any incidents affecting Azure Blob Storage or Networking in your region.
3. If there is an ongoing incident, wait for Microsoft to resolve it before retrying.

1.6 Ask Your Network Administrator

Contact your network or IT administrator and request confirmation of the following:

• Outbound TCP connections on port 22 are allowed to tngsftp.blob.core.windows.net.
• No DPI (Deep Packet Inspection) or application-layer firewall is blocking SSH/SFTP traffic.
• No IP allow-lists or geo-restrictions are preventing access to Azure endpoints.
• DNS resolution for tngsftp.blob.core.windows.net returns a valid IP address.

2. Quick Connectivity Test (All Platforms)

Before proceeding to OS-specific sections, run this quick test from any terminal or command prompt to check basic network reachability:

# Check DNS resolution
nslookup tngsftp.blob.core.windows.net

# Test port 22 connectivity (works on Windows 10+, macOS, Linux)
ssh -v -o ConnectTimeout=10 tngsftp.blob.core.windows.net

3. Windows Troubleshooting

3.1 Check Windows Firewall

1. Press Win + R, type wf.msc, and press Enter to open Windows Firewall with Advanced Security.
2. Click Outbound Rules in the left panel.
3. Look for any rule that blocks port 22 or blocks FileZilla (filezilla.exe).
4. If a blocking rule exists, either disable it or create an allow rule for FileZilla on port 22.

Alternatively, temporarily disable Windows Firewall for testing (re-enable after):

# Run in PowerShell as Administrator
Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled False

# Re-enable after testing
Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled True

3.2 Test Port 22 with PowerShell

# PowerShell - Test TCP connection to port 22
Test-NetConnection -ComputerName tngsftp.blob.core.windows.net -Port 22

Expected successful output:

TcpTestSucceeded : True

3.3 Check DNS Resolution

# Command Prompt or PowerShell
nslookup tngsftp.blob.core.windows.net

# If DNS fails, try with public DNS
nslookup tngsftp.blob.core.windows.net 8.8.8.8

If the public DNS works but your default DNS does not, configure your network adapter to use 8.8.8.8 (Google) or 1.1.1.1 (Cloudflare) as DNS.

3.4 Check for Antivirus / Security Software Interference

Third-party antivirus and security suites (Kaspersky, Norton, Bitdefender, ESET, etc.) often include their own firewall or network filter that can block SFTP:

• Temporarily disable the antivirus firewall module and retry.
• Check the antivirus logs for any blocked connection to port 22 or tngsftp.blob.core.windows.net.
• Add FileZilla as a trusted application in your antivirus settings.

3.5 Check Windows SSH Client

Windows 10/11 has a built-in SSH client. Test direct SFTP from the command line:

sftp tngsftp.<your_user>@tngsftp.blob.core.windows.net

If this works but FileZilla does not, the issue is within FileZilla configuration. Reinstall FileZilla or reset its settings via Edit > Settings > Reset.

3.6 Check Hosts File

Verify that the hosts file does not contain an override for the SFTP server:

type C:\Windows\System32\drivers\etc\hosts

Ensure there is no line redirecting tngsftp.blob.core.windows.net to a different IP or to 127.0.0.1.

4. macOS Troubleshooting

4.1 Test Port Connectivity

# Terminal
nc -zv tngsftp.blob.core.windows.net 22

Expected output on success:

Connection to tngsftp.blob.core.windows.net port 22 [tcp/ssh] succeeded!

If it fails with a timeout, port 22 is blocked by your network.

4.2 Check macOS Firewall

1. Open System Settings (or System Preferences on older macOS).
2. Go to Network > Firewall.
3. If the firewall is enabled, click Options (or Firewall Options) and ensure FileZilla is listed as Allow incoming connections.
4. For testing purposes, you can temporarily disable the firewall, test the connection, then re-enable.

From Terminal:

# Check firewall status
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --getglobalstate

# Temporarily disable (re-enable after testing)
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setglobalstate off

# Re-enable
sudo /usr/libexec/ApplicationFirewall/socketfilterfw --setglobalstate on

4.3 Check DNS Resolution

# Check current DNS resolution
dig tngsftp.blob.core.windows.net

# Test with public DNS
dig @8.8.8.8 tngsftp.blob.core.windows.net

If the default DNS fails, change DNS in System Settings > Network > Wi-Fi > Details > DNS. Add 8.8.8.8 and 1.1.1.1.

4.4 Test SFTP from Terminal

sftp tngsftp.<your_user>@tngsftp.blob.core.windows.net

If this succeeds but FileZilla fails, try resetting FileZilla preferences by deleting its configuration directory:

rm -rf ~/.config/filezilla

Then relaunch FileZilla and re-enter your credentials.

4.5 Check /etc/hosts

cat /etc/hosts

Ensure no entries override tngsftp.blob.core.windows.net.

4.6 Check for Proxy or Content Filter Software

macOS users sometimes have content filter or security software installed (e.g. Little Snitch, Lulu, corporate MDM profiles):

• Check if Little Snitch or Lulu is blocking outgoing connections from FileZilla.
• Check System Settings > General > Profiles for any corporate MDM configuration profiles that may restrict network access.
• Temporarily disable such software to test the connection.

5. Linux Troubleshooting

5.1 Test Port Connectivity

# Using netcat
nc -zv tngsftp.blob.core.windows.net 22

# Alternative: using nmap (install if needed: sudo apt install nmap)
nmap -p 22 tngsftp.blob.core.windows.net

If the port is filtered or closed, a firewall between you and Azure is blocking the connection.

5.2 Check Local Firewall (iptables / nftables / ufw)

# Check ufw status (Ubuntu/Debian)
sudo ufw status verbose

# If ufw is active, allow outbound SSH
sudo ufw allow out 22/tcp

# Check iptables directly
sudo iptables -L OUTPUT -n -v | grep -i "22\|ssh"

# Check for firewalld (RHEL/CentOS/Fedora)
sudo firewall-cmd --list-all

If iptables or firewalld is blocking port 22 outbound, add an allow rule or temporarily disable the firewall for testing:

# Temporarily disable ufw
sudo ufw disable

# Temporarily disable firewalld
sudo systemctl stop firewalld

[[warning=Important]]Remember to re-enable your firewall after testing.[[warning]]

5.3 Check DNS Resolution

# Check resolution
dig tngsftp.blob.core.windows.net

# Or use host
host tngsftp.blob.core.windows.net

# Test with public DNS
dig @8.8.8.8 tngsftp.blob.core.windows.net

If the default DNS resolver fails, temporarily switch by editing /etc/resolv.conf:

sudo cp /etc/resolv.conf /etc/resolv.conf.bak
echo 'nameserver 8.8.8.8' | sudo tee /etc/resolv.conf

Remember to restore the backup after testing.

5.4 Test SFTP from Terminal

# Verbose SFTP connection
sftp -v tngsftp.<your_user>@tngsftp.blob.core.windows.net

The -v flag provides verbose output that shows the SSH handshake process.

5.5 SSH Known Hosts Conflict

If you get a host key verification error, the server fingerprint stored locally may be outdated:

# Remove old key
ssh-keygen -R tngsftp.blob.core.windows.net

# Retry the connection and accept the new key
sftp tngsftp.<your_user>@tngsftp.blob.core.windows.net

5.6 Check /etc/hosts

cat /etc/hosts

Ensure no entries redirect tngsftp.blob.core.windows.net to a wrong IP.

5.7 SELinux (RHEL/CentOS/Fedora)

On systems with SELinux enforcing, it may prevent FileZilla from making outbound connections:

# Check SELinux status
getenforce

# Temporarily set to permissive for testing
sudo setenforce 0

# Check audit log for denials
sudo ausearch -m avc -ts recent | grep filezilla

6. FileZilla-Specific Troubleshooting

6.1 Enable Logging

FileZilla can produce a detailed debug log that helps identify the exact failure point:

1. In FileZilla, go to Edit > Settings > Logging.
2. Check Show debug messages and set the level to maximum (Debug).
3. Attempt the connection and review the log output in the top panel.

6.2 Reset FileZilla Host Key Cache

If FileZilla shows a host key warning or error:

1. Go to Edit > Settings > SFTP.
2. Under Host keys, find and remove the entry for tngsftp.blob.core.windows.net.
3. Reconnect and accept the new host key when prompted.

6.3 Update FileZilla

Ensure you are using the latest version of FileZilla. Older versions may have compatibility issues with Azure Blob Storage SFTP. Download the latest version from https://filezilla-project.org.