Knowing these ports can help you work more efficiently. Simple Network Management Protocol (SNMP) Internet Message Access Protocol (IMAP) Management of Digital Mail Post Office Protocol (POP3) used by e-mail clients to retrieve e-mail from a server Hypertext Transfer Protocol (HTTP) used in World Wide Web Simple Mail Transfer Protocol (SMTP) E-mail Routing Telnet - Remote login service, unencrypted text messages Here are some of the most common ones:įile Transfer Protocol (FTP) Data Transferįile Transfer Protocol (FTP) Command Control The Internet Assigned Numbers Authority (IANA) has assigned port numbers to commonly used services like SSH, FTP, HTTP, HTTPS, and others. You may use the -p option to specify another port number otherwise, SSH will default to 22. In this example, -v stands for verbose, and you should see output similar to this: debug1: Connecting to port 22Īs shown, SSH is trying to connect to using port number 22. For example, to connect to the host via SSH, I would use this command: ssh -v Well-known ports (also known as system ports) are numbered from 0 through 1023. Port numbers are divided into three ranges: well-known ports, registered ports, and dynamic or private ports. Other services use this port number to communicate with the service or app. Through the use of tools like NMAP, you can figure out which ports are open on your Linux system, stop unwanted and unused services, and possibly close those ports altogether with iptables. Ports are identified with positive 16-bit unsigned integers, ranging from 0 to 65535. Linux systems are built to be servers, so attackers would attempt to use a compromised system that way, even if that system was set up to be a desktop.
In simple terms, if a software application or service needs to communicate with others, it will expose a port. It is also possible for different services running on the same computer to expose various ports and communicate with one another using these ports. When a computer system seeks to connect to another computer, the port serves as a communication endpoint. Witin computer networking, ports serve a similar purpose. 10 command-line tools for data analysis in Linux.Running Kubernetes on your Raspberry Pi.A practical guide to home automation using open source tools.6 open source tools for staying organized.An introduction to programming with Bash.A guide to building a video game with Python.