# How to check if FTP port 21 is blocked > Find out how to test whether FTP port 21 is blocked on your network using the command line on Windows or Mac. Source: https://www.kualo.com/knowledgebase/cpanel-files-ftp/how-to-check-if-ftp-port-21-is-blocked Updated: 2026-06-11 --- If you cannot connect to your FTP server, your ISP or company firewall may be blocking port 21. You can test this quickly from the command line. :::info Telnet is used here purely as a connectivity test. On Windows, you may need to enable the Telnet client before running the command (see below). ::: ## Windows 1. Press **Windows key + R** to open the Run dialog, type `cmd`, and press Enter. 2. In the Command Prompt window, run: ```bash telnet yourdomain.com 21 ``` Replace `yourdomain.com` with your actual domain name. :::info If you see the error "telnet is not recognised", you need to enable the Telnet client first. Go to **Control Panel > Programs > Turn Windows features on or off**, tick **Telnet Client**, and click OK. ::: ## Mac 1. Open **Finder**, go to **Applications > Utilities**, and open **Terminal**. 2. Run: ```bash telnet yourdomain.com 21 ``` Replace `yourdomain.com` with your actual domain name. :::info On macOS High Sierra and later, Telnet is not installed by default. You can install it via Homebrew (`brew install telnet`), or use `nc -zv yourdomain.com 21` as an alternative. ::: ## Interpreting the results If port 21 is open and reachable, you will see a response similar to: ``` 220---------- Welcome to Pure-FTPd [TLS] ---------- 220-You are user number 5 of 50 allowed. 220-Local time is now 03:35. 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 see anything else - such as a timeout, connection refused, or no output at all - port 21 is likely being blocked. - If you are on a home connection, contact your ISP and ask them to unblock port 21. - If you are on a work or office network, speak to your network administrator. - As an alternative, ask your FTP client to connect using **passive mode on port 21**. If you are still having trouble, contact Kualo support and we will be happy to help. --- _Source: Kualo Knowledgebase — https://www.kualo.com/knowledgebase/cpanel-files-ftp/how-to-check-if-ftp-port-21-is-blocked · © Kualo Ltd._