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Port 23 (Telnet) — What It Is and How to Use It

Port 23 is the standard port for Telnet, a protocol used for establishing a text-based, unencrypted communication channel between a client and a server. It allows users to remotely access and control a device or server, but due to its lack of encryption, it's largely considered insecure for modern use.

Last updated: 2026-06-11

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Port Number 23
Protocol Telnet

Common Use Cases

  • Accessing legacy systems that do not support SSH
  • Initial configuration of network devices before SSH is enabled
  • Troubleshooting network connectivity issues (though better tools exist)

Interactive Command Builder

nc -zv example.com 23

Check if Port 23 is Open

netstat -ant | grep ":23 "
Get-NetTCPConnection | Where-Object {$_.LocalPort -eq 23}
⚠️ Security Note: Telnet transmits data, including usernames and passwords, in plaintext, making it vulnerable to eavesdropping and credential theft. It should be disabled or replaced with SSH whenever possible.

Related Ports

Port 22 Port 80 Port 443

Frequently Asked Questions

Is port 23 dangerous to leave open?

Yes, leaving port 23 open is highly dangerous. Because Telnet transmits data in plaintext, attackers can easily intercept sensitive information like usernames and passwords. It's strongly recommended to disable Telnet and use SSH instead.

What service uses port 23?

The Telnet service uses port 23. This service provides a command-line interface for remote access to a server or device.