📝 SNMP overview how it works (10 MCQs)

📖 From Data Communication and Networks • 27. Network Management • 10 questions available

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What is SNMP overview how it works?

SNMP works by having a manager send GET, SET, or TRAP messages to agents on network devices; agents retrieve or modify data from their local MIB and respond with the requested information or confirm changes, enabling real-time monitoring and remote configuration.

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📝 All SNMP overview how it works MCQs

Q1. In the loop, after each successful recv call the code executes `maxLen -= n;`. What is the immediate logical consequence of this statement for the next iteration?

A.The buffer size for the next recv increases

B.The buffer size for the next recv remains unchanged

C.The buffer size for the next recv decreases by the number of bytes just received ✅

D.The program terminates

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: The statement reduces `maxLen` by the number of bytes already stored in the buffer (`n`). Consequently, the next call to `recv` can request only the remaining portion of the buffer, preventing overflow and ensuring that only unwritten space is used.

Q2. Which function is used to terminate the socket connection after the echo operation completes?

A.close(s) ✅

B.shutdown(s, SHUT_RDWR)

C.exit(0)

D.free(s)

💡 Difficulty: easy | ✅ Correct: A

📖 Explanation: The code fragment ends with `close(s);`, which releases the file descriptor associated with the socket. Closing the socket is the standard way to end a TCP connection after all data has been processed, making option A the correct choice.

Q3. How does the TCP echo server differ from a UDP echo server in terms of connection handling within the shown code?

A.TCP uses `listen` and `accept` to establish a persistent connection, while UDP does not require these calls

B.TCP sends data with `sendto`, whereas UDP uses `send`

C.Both protocols require the same sequence of `bind`, `recv`, and `send` calls

D.TCP automatically guarantees ordered delivery, so no additional code is needed ✅

💡 Difficulty: easy | ✅ Correct: D

📖 Explanation: TCP requires an explicit connection setup (`listen` and `accept`) before data exchange, unlike UDP which is connectionless. The presented TCP server therefore includes these extra steps to manage a reliable, stateful session, distinguishing it from a UDP implementation.

Q4. What principle does the line `send(s, buffer, len, 0);` illustrate in the context of an echo server?

A.Echoing the exact number of bytes received back to the client

B.Compressing the data before transmission ✅

C.Encrypting the buffer before sending

D.Discarding the received data

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The `send` call uses the variable `len`, which holds the total number of bytes accumulated from successive `recv` operations. By transmitting exactly `len` bytes from `buffer`, the server mirrors the client’s input, embodying the fundamental echo‑server principle of returning the same data it received.

Q5. If `recv` returns 0 during the loop, what can be logically inferred about the client’s state and the server’s subsequent actions?

A.The client has gracefully closed its sending side, causing the loop to exit and the server to send back the data collected so far ✅

B.The client is still sending data, and the server will continue receiving

C.An error occurred, and the server will retry the `recv` call

D.The server will immediately close the socket without sending any data

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: A return value of 0 from `recv` signals an orderly shutdown from the peer, meaning no more data will arrive. The loop condition fails, the server proceeds to the `send` statement to echo the bytes already stored, and then closes the socket.

Q6. Why does the code increment the pointer `ptr += n;` after each successful receive operation?

A.To advance the write position so subsequent bytes are stored after the previously received data ✅

B.To reset the pointer back to the start of the buffer

C.To point to the next socket descriptor

D.To calculate the total number of bytes received

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Increasing `ptr` by `n` moves the pointer past the bytes just placed in the buffer, ensuring that the next `recv` writes into the next free region. This prevents overwriting earlier data and maintains a contiguous record of all bytes received.

Q7. How does the variable `len` relate to the total number of bytes echoed back to the client?

A.`len` accumulates the sum of all bytes received across loop iterations and is used as the length argument in `send`

B.`len` stores the maximum buffer size allowed

C.`len` counts the number of recv calls made ✅

D.`len` is unrelated to the amount of data sent

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Each time data is read, `len += n;` adds the newly received count to the running total. When the loop ends, `len` precisely represents the number of bytes stored in `buffer`, which is then supplied to `send` to ensure the client receives exactly what was received.

Q8. Suppose `recv` returns –1 due to a transient network error. What is the logical outcome for the while‑loop and the subsequent echo operation?

A.The loop condition fails, the loop exits, and the server proceeds to `send` whatever data has been accumulated so far

B.The loop continues indefinitely, repeatedly calling `recv`

C.The server immediately terminates without sending any data

D.The error is ignored and `n` is treated as zero ✅

💡 Difficulty: hard | ✅ Correct: D

📖 Explanation: A negative return from `recv` causes the condition `while ((n = recv(...)) > 0)` to evaluate false, breaking out of the loop. The code then reaches the `send` call, which will transmit any bytes already stored in `buffer`; the error does not trigger a retry within this snippet.

Q9. In what way does using `send(s, buffer, len, 0);` differ from using a low‑level `write(s, buffer, len);` call in this TCP echo server?

A.`send` allows specification of flags (the fourth argument) while `write` does not ✅

B.`write` guarantees atomic transmission, whereas `send` does not

C.`send` can only be used with UDP sockets

D.`write` automatically closes the socket after transmission

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The `send` function includes an extra flags parameter, giving the programmer flexibility to modify transmission behavior (e.g., MSG_DONTWAIT). The `write` system call lacks this parameter, making `send` the more versatile choice for socket I/O, especially when special transmission options might be required.

Q10. If the server receives data in several small fragments (e.g., 10 bytes, then 15 bytes, then 5 bytes), how should it ensure that the entire message is echoed back correctly?

A.Accumulate each fragment’s size in `len` and adjust `ptr` and `maxLen` after every `recv` so that `send` later transmits the full `len` bytes ✅

B.Send each fragment immediately after it is received

C.Ignore fragments smaller than 20 bytes

D.Close the connection after the first fragment

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: By updating `len`, moving `ptr`, and decreasing `maxLen` after each partial read, the server builds a continuous buffer containing all fragments. When the loop ends, `send` uses the final `len` value, guaranteeing that the concatenated message—regardless of how it arrived—is echoed back in its entirety.

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