Port checker

Check state of port on IP address or host name

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Not shown: closed

Not shown: open

Not shown: filtered


What this tool can

Port checker is useful tools for checking state of port on your web server.
You input a IP address/host name and range of port, the lists service name, port number, and state is displayed.

The meanings of port state:

open:TCP connections are being accepted on that port or there is some UDP or SCTP associations on that port.
closed: That port responding to packets sent by the this tool, however no application is listening on that port.
filtered:The packets are sent to that port, however packet filtering (e.g., firewall) prevents the packets from reaching that port.
unfiltered:That port is accessible, but unable to determine whether it is open or closed.
open|filtered:Unable to determine whether that port is open or filtered.
closed|filtered:Unable to determine whether that port is closed or filtered.

Most Commonly used ports you should know:

20 - File Transfer Protocol (FTP) Data Transfer
21 - File Transfer Protocol (FTP) Command Control
22 - Secure Shell (SSH)
23 - Telnet - Remote login service, unencrypted text messages
25 - Simple Mail Transfer Protocol (SMTP) E-mail Routing
53 - Domain Name System (DNS) service
80 - Hypertext Transfer Protocol (HTTP) used in World Wide Web
110 - Post Office Protocol (POP3) used by e-mail clients to retrieve e-mail from a server
119 - Network News Transfer Protocol (NNTP)
123 - Network Time Protocol (NTP)
143 - Internet Message Access Protocol (IMAP) Management of Digital Mail
161 - Simple Network Management Protocol (SNMP)
194 - Internet Relay Chat (IRC)
443 - HTTP Secure (HTTPS) HTTP over TLS/SSL

Useful for

・Checking port forwarding setup on a web server. For example, if you're facing connection issue with a application 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.
・Checking open ports for avoid any external attacks on your web server. Mostly the attackers search a wide range of IPs and request them on different ports to check vulnerability to attack. So, you should only keep those ports open if secured by your Software or Hardware Firewall or an Anti-virus program.

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