> For the complete documentation index, see [llms.txt](https://cybersec.th4ntis.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cybersec.th4ntis.com/networking/common-ports-and-protocols.md). # Common Ports and Protocols Common TCP Ports: * 21 - FTP - File Transfer Protocol * 22 - SSH - Secure Shell * 23 - Telnet * 25 - SMTP - Simple Mail Transfer Protocol * 53 - DNS - Domain Name System * 80 - HTTP - Hyper Text Transfer Protocol * 443 - HTTPS - Hyper Text Transfer Protocol Secure * 110 - POP3 - Post Office Protocol * 139/445 - SMB - Secure Message Block / Samba * 143 - IMAP - Internet Message Access Protocol * 389 - LDAP - Lightweight Direcotry Access Protocol (Both TCP and UDP) * 990 - FTPS - FTP over TLS/SSL * 3306 - MySQL * 3389 - RDP - Remote Desktop Protocol Common UDP Ports: * 53 - DNS - Domain Name System * 67/68 - DHCP - Dynamic Host Configuration Protocol * 69 - TFTP - Trivial File Transfer Protocol * 123 - NTP - Network Time Protocol * 161 SNMP - Simple Network Management Protocol \*Note:\* some ISPs(Comcast) block port 25(SMTP) for residential and some commercial by default so sometimes they will change it to Port 587. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://cybersec.th4ntis.com/networking/common-ports-and-protocols.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.