What is an online port checker tool?

2 min readAug 8, 2020

The open port checker is simple and free online tools you can use to look at your external IP address and find open ports in your computer/device, frequently beneficial in analyzing port forwarding settings on a router. For example, suppose you are facing connection problems using a program (email, IM client, etc.), it might be possible that the interface needed by the application is getting blocked from the router firewall or your ISP. In these instances, this tool may help you in diagnosing any issue using firewall installment. You might also find this helpful for safety purposes if you’re unsure whether a specific port is closed or open.

This tool may also be utilized as a port scanner to scan your system for ports that are generally forwarded. It’s essential to be aware that a few ports, such as port 25, are usually blocked at the ISP level in an effort to stop malicious activity.

Most Commonly Used Ports

Port figures ranges from 1 to 65535out of that well known ports are pre-defined as convention from IANA.

. 0–1023 — Well known ports (HTTP, SMTP, DHCP, FTP etc.)

· 1024–49151 — Reserved Ports

· 49152–65535 — Dynamic/Private Ports

Common ports are :

  • 21 FTP
  • 22 SSH
  • 23 TELNET
  • 25 SMTP
  • 53 DNS
  • 80 HTTP
  • 110 POP3
  • 115 SFTP
  • 135 RPC
  • 139 NetBIOS
  • 143 IMAP
  • 194 IRC
  • 443 SSL

Understanding Port Forwarding :-

Port forwarding or port mapping entails translating the address (or port number to a new destination), requiring the packets, and forwarding it. It is typically utilized in linking remote computers to specific programs running on the pc (in a private LAN (Local Area Network)). For example: running a public server (HTTP, port 80) onto a pc in a private LAN or allowing SSH access to a particular computer in a private LAN, etc.




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