Task:
From your host at 10.0.0.1, connect to the remote host at 10.0.0.2 on port 31337, and then shutdown the connection after you’re done sending data.

🧠 Understanding the Challenge

The server waits to receive all data from the client. It only sends back the flag when it sees the client has closed its sending side (EOF). This is common in protocols where the server must process all input before responding.

We cannot simply send a string like "END" because:

  • Network packets might be fragmented or merged.
  • "END" could appear in actual data, causing confusion.

Instead, we signal the end of input cleanly by shutting down the socket for writing — this is equivalent to closing stdin.

🛠️ Solution with Netcat

We use the -N option with netcat (if supported), which tells nc to close the connection properly after reaching EOF on stdin.

✅ Command:

nc -N 10.0.0.2 31337

If -N isn’t supported, you can connect with nc 10.0.0.2 31337, then press Ctrl-D manually to send EOF.

Example Output

root@ip-10-0-0-1:~# nc -N 10.0.0.2 31337
pwn.college{3ndlY_ShUtDoWn_ExPlIcIt}