FTP Server Test Online Tool

Technical Details

Check connection, authentication, encryption, and mode negotiation of any File Transfer Protocol (FTP) server over IPv4 and IPv6. Verify your server's security and port configuration.

The connection mode determines how data channels are established through firewalls and NAT. In Passive Mode, the server opens a random port for the client. The client uses the EPSV (Extended Passive) command for IPv6 and IPv4, automatically falling back to the classic PASV command if the IPv4 server rejects it. In Active Mode, the client opens a port and waits for the server using the EPRT (for IPv6) or PORT (for IPv4) commands. Active mode is frequently blocked by modern client-side routers.

FTP transmits credentials in plaintext by default. Securing the protocol with SSL/TLS transforms it into FTPS (FTP Secure). TLS disabled performs a standard unencrypted connection, which should be avoided in production environments where FTPS is strictly recommended. TLS enabled attempts an opportunistic explicit TLS upgrade (FTPES). TLS forced guarantees strict encryption, immediately aborting the connection if the server rejects the AUTH TLS handshake. Both encrypted modes require an SSL/TLS certificate configured on the server. Self-signed certificates are fully supported by this test.

It sends an NLST command to perform a directory listing, which works seamlessly for testing standard FTP servers (Linux, Windows, FreeBSD, Unix) and network devices, such as embedded devices, routers, switches, firewalls, Network Attached Storage (NAS), IP cameras, Digital Video Recorders (DVR), dedicated hardware appliances, and all FTP servers in general. The network test is considered successful as long as it receives a 150 status code, confirming the server is ready to open the data connection and the firewall is properly configured, even if a subsequent 226 code fails due to file system permissions.

FTP Log Interpretation

The output console displays the raw communication over the FTP control channel between our diagnostic node and your target server. Reading this transcript is the most effective way to troubleshoot authentication errors, TLS handshakes, and NAT or firewall misconfigurations. Use the following legend to interpret the data flow:

---> Outbound Commands: These lines show the exact commands our diagnostic tool sent to your server (e.g., USER, PASS, PORT).
<--- Inbound Responses: These lines display the raw replies and standard status codes returned by your server (e.g., 220 Welcome, 331 Password required, 150 Opening data connection).
---- Internal Client Status: These lines indicate actions performed locally by our testing tool, such as resolving DNS, opening data sockets, or detecting the end of a file (EOF).
TLS/SSL Verification: Lines without a prefix (e.g., Certificate, Issued by, Trusted) appear during encrypted connections and display the local validation of your server's certificate chain.

Common Connection Issues

The following steps may help you pass this test in case of trouble:

Verify that your server and FTP service are up and running.
Verify that the domain's DNS is resolving to the correct IP addresses, if you're entering a hostname.
Verify that your server's control port (usually TCP 21) is accessible from this website's IPv4 and IPv6 addresses: 173.249.29.54 and 2a02:c207:1:3253:1::1
Verify that your firewall allows passive mode connections by opening the configured passive port range (e.g., 49152-65535 or your custom range).
Verify that your firewall allows active mode connections by permitting outbound traffic from your server's TCP data port (usually 20).

Save Your Results

You can optionally save your results and share them with your team as evidence for troubleshooting tickets, scientific documentation, IT compliance audits, or any other purpose. This helps satisfy the strict evidence and network monitoring requirements of major cybersecurity frameworks such as ISO 27001, SOC 2, PCI DSS, and HIPAA. We commit to storing your results for a minimum period of 5 years and a maximum of 10 years, after which the saved results are permanently deleted from our servers.

For strict security, no login credentials are ever stored.

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