FTP (File Transfer Protocol) – TCP/21
Purpose: Used for transferring files between clients and servers.
Command:
ftp <server-ip>
SSH (Secure Shell) – TCP/22
Purpose: Provides a secure channel for remote login and command execution.
Command:
ssh username@<server-ip>
Telnet – TCP/23
Purpose: Offers unencrypted, text-based remote login.
Command:
telnet <server-ip>
SMTP (Simple Mail Transfer Protocol) – TCP/25
Purpose: Responsible for sending email from clients to mail servers and between mail servers.
Command:
telnet <mail-server-ip> 25
DNS (Domain Name System) – UDP/TCP/53
Purpose: Translates human-friendly domain names into IP addresses (and vice versa).
Command:
nslookup example.com
DHCP Server – UDP/67
Purpose: Assigns IP addresses and network configuration parameters to DHCP clients.
Command:
dhclient -v
DHCP Client – UDP/68
Purpose: Used by client machines to receive IP address leases and network settings from the DHCP server.
Command:
dhclient -r
HTTP (Hypertext Transfer Protocol) – TCP/80
Purpose: Primary protocol for transferring web pages and related data.
Command:
curl http://example.com
POP3 (Post Office Protocol v3) – TCP/110
Purpose: Retrieves emails from a remote mail server to a local client.
Command:
telnet <mail-server-ip> 110
NTP (Network Time Protocol) – UDP/123
Purpose: Synchronizes the clocks of computers over a network.
Command:
ntpdate <ntp-server-ip>
NetBIOS – TCP/139
Purpose: Allows applications on different computers to communicate within a LAN.
Command:
nmblookup -A <ip-address>
IMAP (Internet Message Access Protocol) – Typically TCP/143
Purpose: Retrieves and manages email on a mail server.
Command:
telnet <mail-server-ip> 143
HTTPS (Secure HTTP) – TCP/443
Purpose: Secured version of HTTP, encrypting data in transit with SSL/TLS.
Command:
curl https://example.com
SMB (Server Message Block) – TCP/445
Purpose: Provides file and printer sharing services primarily on Windows networks.
Command:
smbclient -L <server-ip>
Oracle Database – TCP/1521
Purpose: Default listener port for Oracle Database connections.
Command:
sqlplus username/password@<oracle-server-ip>:1521/service_name
MySQL – TCP/3306
Purpose: Default port for MySQL database communication.
Command:
mysql -h <mysql-server-ip> -u username -p
RDP (Remote Desktop Protocol) – TCP/3389
Purpose: Remote desktop access to Windows-based systems.
Command:
xfreerdp /v:<windows-ip> /u:username /p:password
PostgreSQL – TCP/5432
Purpose: Default port for PostgreSQL database connections.
Command:
psql -h <postgres-server-ip> -U username -d database_name
What Undercode Say
Understanding and managing network ports is fundamental for IT professionals, as they form the backbone of secure and efficient communication across systems. From file transfers using FTP (TCP/21) to secure remote logins via SSH (TCP/22), each port serves a unique purpose in maintaining seamless operations. For instance, DNS (UDP/TCP/53) ensures domain names are resolved to IP addresses, while HTTPS (TCP/443) encrypts web traffic, safeguarding sensitive data.
In Linux, commands like nslookup, ssh, and `curl` are indispensable for troubleshooting and interacting with these services. Windows users rely on tools like `smbclient` for SMB file sharing and `xfreerdp` for remote desktop access. Database administrators frequently use `mysql` and `psql` to manage MySQL and PostgreSQL databases, respectively.
For secure email communication, protocols like SMTP (TCP/25) and IMAP (TCP/143) are essential, while NTP (UDP/123) ensures system clocks remain synchronized. Network administrators must also be familiar with DHCP (UDP/67/68) for IP address management and NetBIOS (TCP/139) for legacy LAN communication.
Mastering these ports and their associated commands not only enhances system administration skills but also strengthens cybersecurity practices. For further reading, consider exploring resources like IANA’s port assignments and Linux man pages.
By leveraging these tools and protocols, IT professionals can ensure robust, secure, and efficient network operations, paving the way for seamless digital experiences.
References:
Hackers Feeds, Undercode AI
