FTPMonitor / Guides / FTP directory listing timeout

FTP directory listing timeout

Why FTP directory listings hang or timeout and how to resolve passive mode firewall problems.

Diagnose this automatically

Test whether the server allows directory listing with valid credentials.

terminal
npx ftpmonitor check --protocol ftp --host ftp.example.com --port 21 --username user --password pass --path /incoming
Shareable output
terminal
npx ftpmonitor check --protocol ftp --host ftp.example.com --port 21 --username user --password pass --path /incoming --format slack --copy

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

Directory listing timeouts occur when the FTP data channel cannot be established.

Common causes

  • Passive mode ports blocked
  • Incorrect firewall configuration
  • NAT misconfiguration
  • Server returning private IP in PASV response

Fix checklist

  1. Ensure passive ports are open.
  2. Verify PASV configuration on the server.
  3. Check NAT configuration.
  4. Confirm server advertises correct public IP.
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