If you've ever spent an hour troubleshooting a file transfer problem, you probably know the routine:
- Is DNS resolving correctly?
- Is the port actually open?
- Is SSH responding?
- Did the server certificate expire?
- Did someone change the SSH fingerprint?
- Does the FTP server support TLS?
- What does that mysterious FEAT response actually mean?
Over the years I've found myself repeatedly opening terminal windows, running DNS lookups, checking certificates, testing ports and verifying FTP or SFTP configurations.
Most of these tasks are simple, but they often require a mix of command-line tools and platform-specific utilities.
So we decided to build a collection of small browser-based diagnostic tools that make these checks available from anywhere.
The Tools
FTP Connection Test
Performs a real FTP/FTPS connectivity test and checks:
DNS resolution
TCP connectivity
FTP authentication
PASV support
FTP FEAT capabilities
FTPS support
TLS certificate information
Anonymous login availability
SFTP Connection Test
Verifies SSH and SFTP configuration by checking:
SSH banner
Authentication
Host key information
SSH fingerprint
SFTP subsystem availability
DNS Checker
Retrieves common DNS records including:
A records
AAAA records
MX records
TXT records
NS records
Reverse DNS
Useful when troubleshooting hosting migrations, email issues and DNS propagation.
TLS Certificate Checker
Checks:
Certificate issuer
Expiration date
Days remaining
Common name
SAN entries
TLS protocol version
SSH Fingerprint Lookup
Quickly retrieve:
Host key algorithm
SHA256 fingerprint
Public host key
Security information
Useful when validating SSH or SFTP servers.
FTP Port Checker
Tests common ports used by:
FTP (21)
SFTP (22)
HTTP (80)
HTTPS (443)
FTPS (990)
Unlike a simple TCP connect test, it also attempts basic protocol validation.
FTP Feature Decoder
Paste a FEAT response and get human-readable explanations for:
AUTH TLS
MDTM
MLST
UTF8
MODE Z
REST STREAM
MFMT
and many other FTP extensions.
Why We Built Them
The original goal wasn't to create a public tool collection.
We were building and operating FTP, FTPS and SFTP infrastructure and repeatedly needed these checks ourselves while debugging customer environments.
Eventually we realized that many of the same troubleshooting steps are universal, so we cleaned them up and made them publicly available.
Feedback Welcome
We're continuing to add more tools related to FTP, SFTP, DNS, TLS and secure file transfer infrastructure.
If there are diagnostics you find yourself performing regularly, I'd love to hear about them.
You can try the tools here:
Feedback and suggestions are welcome.
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