How to Check if the Default FTP Port 21 is Blocked (2024)

FAQs

How to Check if the Default FTP Port 21 is Blocked? ›

In addition, you can check the status of other ports by replacing the “21” at the end of the command with a different port number. After entering the command, if you see the message “could not open connection to the host, on port 21: connect failed“, then this is showing that the port is being blocked.

FTP Port 21 is the Default Control Port

This is sometimes called the command or control port by default. Then the client makes another connection to the server over port 20 for file transfers to take place. The administrator can change the default port for sending commands and files over FTP.

In Control Panel, click Programs and Features, and then click Turn Windows Features on or off. Expand Internet Information Services, and then FTP Server. Select FTP Service.

TCP port 21 is the default port used by File Transfer Protocol (FTP) to transfer files between systems over a network. An unrestricted inbound access to this port can allow attackers to connect to the FTP server and potentially exploit vulnerabilities, leading to unauthorized access or data exfiltration.

FTP works on TCP port 21. Simply do a telnet to the IP address with port 21 “telnet x.x.x.x 21” or run an NMAP scan : nmap x.x.x.x -p 21.. If the telnet command gives an output as “Connected” or if the NMAP output gives the port as “Open”, the FTP port on that server is Open.

The use of FTP over port 20 and 21 is inherently insecure because traffic passed over them is unencrypted. If security is a concern, you should consider using one of the secure versions of the protocol: Secure File Transfer Protocol (SFTP) over port 22 or File Transfer Protocol Secure (FTPS) over ports 989 and 990.

How do I check my FTP permissions? ›

Access the server preferences in Server Functions > FTP Configuration. On the FTP Users tab, click the name of the user you want to modify. Click Permissions report. Result: The user permissions for all FTP sites are listed.

Perhaps the best-known FTP testing method is a 20-minute time trial. In this format, you ride as hard as you steadily can for 20 minutes; 95% of your average power during this interval is used as your FTP.

When testing for blocked ports, it's important to ensure that the server you're connecting to is actually listening on the given port. This can be confirmed with the “netstat -na” command, where you'll see the port in a LISTENING state, or by testing from another device that is able to connect.

It might be getting blocked by your ISP (internet service provider), or it could be an issue with your security settings. If the issue is related to your security permissions, you'll just need to make sure you allow port 21 access.

File Transfer Protocol (Control Channel)

FTP servers open their machine's port 21 and listen for incoming client connections. FTP clients connect to port 21 of remote FTP servers to initiate file transfer operations.