Monitoring FTP server port 21 / Telnet FTP commands / Check FTP Port  |  26-Mar-2025

FTP monitoring TCP port 21

In many environments it is important to monitor FTP servers. Some options are described here.

Content

► FTP monitoring port 21 with Telnet or Putty

► FTP monitoring port 21 with PortCheck

► FTP monitoring port 21 with PingTool

FTP monitoring port 21 with Telnet or Putty

You can check any FTP Server on FTP port 21 with the following Telnet commands. Open a command line and type: 

telnet ftp-server.domain.com 21

This can also be achieved with the free PuTTY software. Check the "Telnet" radio button and type 21 instead of 23 in the "Port" textbox. In newer PuTTY versions, select "Other" and choose Telnet.

If your server is online a connection will be established on port 21 (FTP). A typical FTP Server answers with the an output like this:

220 ProFTPD Server (FTP server) [::ffff:89.236.73.132]

Now you can communicate with the server by logging in:

user ftp-user123

331 Password required for ftp-user123

pass TreeMonkeyHouse123

230 User ftp-user123 logged in

 

The better way to monitor FTP port 21 (free command line tool, no installation required)

You can check TCP port 21 (and other ports) with the TCP Ping command line tool (www.portcheck-tool.com). It can be used in a similar way to the ping command. Just specify host and TCP port:

PortCheck.exe MyFtpServer 21

or continuous

PortCheck.exe -t MyFtpServer 21

If the server is responding, the line is displayed in green, otherwise in red. The result looks like this:

C:\Users\admin>portcheck -t ftp.domain.com 21 ftp.domain.com - Port 21 - OPEN - 30ms ftp.domain.com - Port 21 - OPEN - 34ms ftp.domain.com - Port 21 - OPEN - 40ms ftp.domain.com - Port 21 - OPEN - 47ms ftp.domain.com - Port 21 - OPEN - 30ms ftp.domain.com - Port 21 - closed ftp.domain.com - Port 21 - closed ftp.domain.com - Port 21 - closed ftp.domain.com - Port 21 - closed ftp.domain.com - Port 21 - OPEN - 30ms ftp.domain.com - Port 21 - OPEN - 29ms ftp.domain.com - Port 21 - OPEN - 41ms ftp.domain.com - Port 21 - OPEN - 33ms ftp.domain.com - Port 21 - OPEN - 38ms ftp.domain.com - Port 21 - OPEN - 32ms ftp.domain.com - Port 21 - OPEN - 34ms ftp.domain.com - Port 21 - OPEN - 30ms

PortCheck offers many additional options like sending e-mails in the case of a failure or notifying with a beep. PortCheck can check multiple hosts on multiple TCP ports with a single command. The PortCheck tool is also part of the PingTool software, which is freeware, too.

...or have a look at PingTool - the adhoc monitoring tool

Ping Tool is more than just another ping tool for Windows 11: It's also a graphical Port Check Tool and a Wake on Lan software for IT professionals. It's a portable tool and it's free!

Some PingTool features:

• Ping GUI software with Ping and TCP port check (TCP ping)

• Wake-On-Lan tool (Magic Packet)

• Perform LAN network speed tests

• Open/Save configurations

• Create custom actions

• ...

 

Have a look at the PingTool overview video on YouTube:

Common TCP ports:

TCP Port 21 - FTP (File Transfer Protocol)
TCP Port 22 - SSH (Secure Shell)
TCP Port 23 - Telnet
TCP Port 25 - SMTP --> article TCP Port Check SMTP 25
TCP Port 80 - HTTP (Hypertext Transfer Protocol)
TCP Port 110 - POP3 (Postoffice Protocol)
TCP Port 135 - DCE / WMI
TCP Port 139 - NetBIOS
TCP Port 143 - IMAP4
TCP Port 443 - HTTPS (Hypertext Transfer Protocol - Secure)
TCP Port 445 - SMB (Server Message Block)
TCP Port 1433 - MS SQL
TCP Port 1494 - ICA (Citrix)
TCP Port 1521 - Oracle
TCP Port 3389 - RDP (Remote Desktop Protocol)
TCP Port 5060 - SIP