How to Check if FTP Port 21 is Blocked

Some local ISPs are blocking the default TCP port for FTP connection – 21, which may cause connection issues. Below you may view how to check if that port is blocked in 3 operating systems:
  1. Windows OS:
    In order to check if port 21 is blocked, click on the “Start Menu”
    Search for “cmd” and press enter to go to "Command Prompt"
    In the newly opened command prompt enter the following command followed by “Enter” button:
    telnet 21

  2. Linux OS:
    In order to check if port 21 is blocked, simply open your favorite shell/terminal and type the following command followed by “Enter” button:
    telnet 21

  3. Apple/Mac OS:
    In order to check if port 21 is blocked, navigate to Mac HD -> “Applications” directory -> Utilities sub-directory. Once the terminal is opened type the following command followed by “Enter”:
    telnet 21
If you receive the following result, that means that port 21 is not blocked from your ISP or your Firewall:
Connected to
Escape character is ‘^]’.
220———- Welcome to Pure-FTPd [privsep] [TLS] ———-
220-You are user number 1 of 50 allowed.
220-Local time is now 07:16. Server port: 21.
220-This is a private system – No anonymous login
220-IPv6 connections are also welcome on this server. 220 You will be disconnected after 15 minutes of inactivity.
If you receive the massage like this, that is mean port 21 is blocked by your local ISP or your Firewall:
telnet: connect to address IP_Address: Connection refused

Then you should review your firewall or contact your local ISP for further assistance.

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