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Check if FTP port 21 is blocked
FTP (File Transfer Protocol) is employed to transfer the files from your local machine to hosting server. FTP by default works on port 21. Your web hosting provider occasionally changes FTP port OR your ISP (Internet Service Provider) blocks it.
To see if it’s being blocked, you can telnet the default FTP port 21 .
Windows OS
Click on Start >> Run OR use a shortcut key Windows + r & type cmd. Hit Enter/Ok & it will open the MS-DOS prompt of your local machine. Usually known as command prompt. Perform a telnet onto port 21 for your domain name.
telnet mydomain.com 21
Linux OS
Open your terminal (the way you have MS-DOS prompt, in linux it is terminal) and perform the command as below to telnet your domain on port 21.
telnet mydomain.com 21
MAC OS
MAC has the terminal the same way you have it for linux. Command to telnet is the same.
telnet mydomain.com 21
When performing a telnet from any of the OS, if the connection is established, you will get output something as below.
220———- Welcome to Pure-FTPd [privsep] [TLS] ———-
220-You are user number 13 of 50 allowed.
220-Local time is now 11:29. Server port: 21.
220 You will be disconnected after 15 minutes of inactivity.
This means FTP port is enabled and service is working. You should be able to upload the files now. If telnet fails, contact your web hosting provider.