Check for open ports and verify port forwarding setup on your router.
What is Port Checker ?
Port Checker is a simple and free online tool for checking open ports on your computer/device, often useful in testing port forwarding settings on a router. For instance, if you're facing connection issues with a program (email, IM client etc) then it may be possible that the port required by the application is getting blocked by your router's firewall or your ISP. In such cases, this tool might help you in diagnosing any problem with firewall setup. You could also find this useful for security purpose, in case you're not sure whether a particular port is open or closed. If you host and play games like Minecraft, use this checker to make sure the server port(25565) is configured properly for port forwarding, then only your friends will be able to connect to your server.
In Ubuntu 18.04, the Port directive of the sshdconfig config file specifies the port number that ssh server listens on. You can check the current configuration with following command: grep -i port /etc/ssh/sshdconfig. The Port directive is commented out by default, which means SSH daemon listens on the default port 22. Linux ssh server configuration is stored in /etc/ssh folder with a name sshdconfig. This configuration file provides a lot of configuration parameters. We can print the current port configuration with the following command by grepping Port text. $ cat /etc/ssh/sshdconfig grep Port. Port 80 is the default port for http traffic. With blocked port 80 you will need to run your web server on a non-standard port. Port 25 is the default port for sending and receiving mail. ISPs block this port to reduce the amount of spam generated by worms on infected machines within their network.
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 - SSL / HTTPS (Hypertext Transfer Protocol Secure)
- 445 - SMB
- 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
- 3306 - MySQL
- 5432 - PostgreSQL
- 5900 - VNC
- 6379 - Redis
- 11211 - Memcached
- 25565- Minecraft
If you're looking for a full list of port numbers check out this wikipedia page. I've listed all the common ports above, feel free to enter any custom port number to check. By default, this site is taking your device's IP address as target ip address (the device through which you're visiting this web page), but you can change the IP input field to check for other IP addresses - remote clients and servers as well. But, please don't misuse this option otherwise, I would have to restrict the IP address to source again (as I had done earlier). Please keep in mind that if you're using a VPN or proxy server then it may not be able to get your device's IP correctly.
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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This tutorial explains how to configure Ubuntu OpenSSH server to run on some specific port number rather than the default port number 22, in order to increase the overall security of your Ubuntu server.
The SSH server on Ubuntu listen on TCP port 22 by default. You can run the netstat command to check ssh port currently running on:
As you can see, the SSH daemon is currently running on TCP port 22.
In Ubuntu 18.04, the Port directive of the sshd_config config file specifies the port number that ssh server listens on. You can check the current configuration with following command:
Check Ssh Port Open
The Port directive is commented out by default, which means SSH daemon listens on the default port 22.
Check Ssh Port Linux
If you want to change the default SSH port in Ubuntu, perform the following steps with root privileges:
- Open the /etc/ssh/sshd_config file and locate the line:
- Then, uncomment (Remove the leading # character) it and change the value with an appropriate port number (for example, 22000):
- Restart the SSH server:
After that, run the netstat command and make sure that the ssh daemon now listen on the new ssh port:
When connecting to the server using the ssh command, you need to specify the port to connect using the -p flag:
Note that if the Firewall is enabled, you need to add a rule to allow new SSH port.