IPA IP 2024 Question 92
A question IPA Japan published in 令和6年度 ITパスポート試験 公開問題 問92, translated into English. ITPEC is based on the same exams.
When one (1) server that is connected to the Internet provides both an e-mail sending and receiving function and a Web access function, which of the following is used by an application program on a terminal to specify to the server which of these functions it uses?
Explanation
Port number — it tells the server which of its applications (services) a request is for.
The IP address, found from the host name or domain name through DNS, identifies the server on the network, and both of its functions share it. Inside the server each service waits on its own port number: for example 25 (SMTP) or 587 for sending mail, 110 (POP3) or 143 (IMAP) for receiving it, and 80 (HTTP) or 443 (HTTPS) for web access. The terminal's application puts the destination port number in the TCP header, and the server hands the data to the program listening on that port.
Answer (c)
Why not others:
- •(a) IP address — identifies the server as a whole; the mail function and the Web function are reached at the same address
- •(b) Domain — the part of a name that identifies an organization or a network, such as
example.; it does not select a serviceco. jp - •(d) Host name — names the computer and is turned into its IP address by DNS, so it too leads to the same server, not to one function
Key rule: The IP address finds the computer; the port number finds the application on it. Together they form the address of one service.
Networks · AI-written, may contain errors
This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.