Port directory — page 7

FTP uses TCP 21 for its control connection. File data travels over a separate connection, so a successful login does not prove transfers will work.

Resource Location Protocol service port for network resource location and discovery

Graphics Protocol service port for graphics data transmission and processing

Host Name Server port for hostname resolution and name services

WHOIS protocol port for domain name and IP address information queries

WHOIS protocol port for domain name and IP address queries

TCP 49 is the registered port for TACACS+ (Terminal Access Controller Access-Control System Plus), the AAA protocol network devices use for centralized authentication, authorization and accounting of admin logins — think Cisco ISE or the open TACACS+ daemon.

Remote Access Protocol port for remote system access and management

TFTP (Trivial File Transfer Protocol) runs on UDP 69 with no authentication and no directory listing. It exists for automated distribution — router firmware, PXE network boot, VoIP phone provisioning — where the client already knows the exact filename.

Gopher protocol port for document retrieval and information browsing

Finger protocol port for user information queries and system status retrieval

HTTP alternative port for web services and HTTP communication

HTTP alternative port for web proxy and caching services

Hostname service port for network hostname resolution

ISO-TSAP (Transport Service Access Point) protocol

TCP/UDP 111 is the ONC RPC portmapper (rpcbind). RPC services such as NFS register here, and clients query 111 to discover the actual service ports. It almost always appears alongside NFS (2049).

UUCP path service port for Unix-to-Unix copy protocol path information

Network News Transfer Protocol port for newsgroup article distribution and retrieval

UDP 137 is the NetBIOS Name Service (NBNS) from the legacy Windows stack — it resolves computer names to IPs. UDP 138 (datagram) and TCP 139 (session) complete the trio. Modern Windows networks rely on DNS plus SMB over 445, leaving 137 as legacy.

NetBIOS datagram service port for Windows network connectionless communication

NetBIOS session service port for Windows file and printer sharing

IRC protocol port for Internet Relay Chat services

Quick Mail Transfer Protocol port for mail transmission and relay services

IPX protocol port for Novell network communication protocol