System

Reserved port；not used（if the sending process does not prepare to accept reply messages，can be used as source port）

TCP Multiplexer service port for multiplexing multiple TCP connections on a single port

Remote Job Entry service port for remote job submission and management

Echo Protocol service port for network connection testing and diagnostics

Discard Protocol service port for network testing and data discarding

Systemstatus display

Daytime Protocol service port for retrieving system date and time information

Network Status Protocol service port for displaying network connection status information

Quote of the Day Protocol service port for providing daily quotes and message services

Message SendingProtocol

Character Generator Protocol service port for generating test character streams

FTP data transfer port for File Transfer Protocol data connections

Simple Mail Transfer Protocol port for mail transmission and routing services

Private printer service port

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

TACACS authentication protocol port for network device authentication and authorization

MTP ，mailtransferprotocol

DHCP server port for Dynamic Host Configuration Protocol

DHCP client port for Dynamic Host Configuration Protocol

Gopher protocol port for document retrieval and information browsing

Finger protocol port for user information queries and system status retrieval