312-50V10 · Question #313
What is the outcome of the comm"nc -l -p 2222 | nc 10.1.0.43 1234"?
The correct answer is B. Netcat will listen on port 2222 and output anything received to a remote connection on 10.1.0.43. This netcat command creates a simple relay: anything received on the local listening port 2222 is piped directly to a remote host at 10.1.0.43 on port 1234.
Question
What is the outcome of the comm"nc -l -p 2222 | nc 10.1.0.43 1234"?
Options
- ANetcat will listen on the 10.1.0.43 interface for 1234 seconds on port 2222.
- BNetcat will listen on port 2222 and output anything received to a remote connection on 10.1.0.43
- CNetcat will listen for a connection from 10.1.0.43 on port 1234 and output anything received to
- DNetcat will listen on port 2222 and then output anything received to local interface 10.1.0.43.
How the community answered
(41 responses)- A5% (2)
- B80% (33)
- C12% (5)
- D2% (1)
Why each option
This netcat command creates a simple relay: anything received on the local listening port 2222 is piped directly to a remote host at 10.1.0.43 on port 1234.
Netcat does not interpret an IP address as a network interface binding in this syntax, and port numbers are not used as durations in seconds.
The '-l -p 2222' flags cause netcat to listen for an inbound connection on port 2222, and the pipe character '|' redirects all data received on that listener to the second netcat process. The second 'nc 10.1.0.43 1234' acts as a client, initiating an outbound connection to 10.1.0.43 on port 1234 and forwarding the piped data to it. This effectively creates a unidirectional TCP relay between two endpoints.
The '-l -p 2222' flag makes netcat listen on the local machine's port 2222, not wait for a connection originating specifically from 10.1.0.43.
10.1.0.43 in this command is a remote destination host for the second netcat process, not a local interface address; the output goes to a remote connection, not the local interface.
Concept tested: Netcat piped relay for traffic forwarding
Source: https://linux.die.net/man/1/nc
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