Port Checker is a simple and free online tool for checking open ports on your computer/device, often useful in testing port forwarding setup on a machine. For instance, if you're facing connection issue with a program (email, IM client etc) then it may be possible that the port required by the application is getting blocked by firewall or ISP. In such cases, this tool might help you in diagnosing the issue. It's also useful for security reasons, in case you're worried whether a particular port is open or closed.
Most Commonly Used Ports
Port numbers ranges from 1 to 65535, out of which well known ports are pre-defined as convention by IANA.
- 0-1023 - Well known ports (HTTP, SMTP, DHCP, FTP etc)
- 1024-49151 - Reserved Ports
- 49152-65535 - Dynamic/Private Ports
Well known ports
- 20 & 21 - FTP (File Transfer Protocol)
- 22 - SSH (Secure Shell)
- 23 - Telnet, a Remote Login Service
- 25 - SMTP (Simple Mail Transfer Protocol)
- 53 - DNS (Domain Name System)
- 80 - HTTP (Hypertext Transfer Protocol)
- 110 - POP3 (Post Office Protocol 3)
- 115 - SFTP (Secure File Transfer Protocol)
- 123 - NTP (Network Time Protocol)
- 143 - IMAP (Internet Message Access Protocol)
- 161 - SNMP (Simple Network Management Protocol
- 194 - IRC (Internet Relay Chat)
- 443 - HTTPS (Hypertext Transfer Protocol Secure)
- 465 - SMTPS (Simple Mail Transfer Protocol over SSL)
- 554 - RTSP (Real Time Stream Control Protocol)
- 873 - RSYNC (RSYNC File Transfer Services)
- 993 - IMAPS (Internet Message Access Protocol over SSL)
- 995 - POP3S (Post Office Protocol 3 over SSL)
- 3389 - RDP (Remote Desktop Protocol)
- 5631 - PC Anywhere
If you're looking for a full list of port numbers check out this wikipedia page.
Understanding Port Forwarding
Port forwarding or port mapping involves translating the address (or port number to a new destination), accepting the packets and forwarding it (using routing table). It's typically used in connecting remote computers to specific programs running on computer (in a private LAN (Local Area Network)). For example : running a public server (HTTP, port 80) on a computer in a private LAN or granting SSH access to a specific computer in a private LAN etc. Read More on Wikipedia.
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