Learn in the textbookTCP/IP and Web Protocols
DefinitionA port number (ポート番号) tells which of the communication applications running on one computer the traffic is for.
ExplanationAn IP address pinpoints a device on the network, while a port number pinpoints the destination application inside that device. Port numbers are handled by TCP and UDP and range from 0 to 65535. Common services have numbers assigned in advance, called well-known ports: HTTP uses 80 and HTTPS uses 443, for example.
AnalogyIt is like mail delivered to a company's address being sorted onto each department's shelf by the department name on it. The address is the IP address, and the department name is the port number.
Memory hookPort means harbor. Ships (data) may reach the same island (device), but the harbor they enter decides which town (application) they go to.