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FTP connection reset by peer

Why FTP connections reset unexpectedly and how to diagnose firewall or server termination issues.

Diagnose this automatically

Test whether the network port is reachable before investigating authentication problems.

terminal
npx ftpmonitor check --protocol ftp --host ftp.example.com --port 21
Shareable output
terminal
npx ftpmonitor check --protocol ftp --host ftp.example.com --port 21 --format slack --copy

Prefer the browser? Run the same check on the homepage.

Connection reset by peer means the remote server closed the connection unexpectedly.

This usually indicates server-side rejection, firewall interruption, or protocol mismatch.

Common causes

  • Server terminated the connection
  • Firewall or IDS dropped the connection
  • Protocol mismatch (FTP vs FTPS)
  • Idle timeout settings

Fix checklist

  1. Verify the correct protocol (FTP vs FTPS).
  2. Check firewall or security device logs.
  3. Confirm the server supports your client connection method.
  4. Try reconnecting using passive mode.
Related
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