FTPMonitor / Guides / FTP transfer stalls

FTP transfer stalls

Why FTP transfers stall mid-transfer and how to troubleshoot data channel issues.

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

FTP transfers may stall when the data channel is interrupted.

Common causes

FTP passive mode firewall issues — Why FTP PASV fails behind firewalls/NAT and how to configure passive ports correctly.
FTP data connection failed — Why FTP data connections fail and how to troubleshoot passive and active data channel issues.
FTP directory listing timeout — Why FTP directory listings hang or timeout and how to resolve passive mode firewall problems.
FTP passive mode not working — Why FTP passive mode fails and how to configure passive ports and NAT correctly.
FTP EPSV error — Understanding FTP EPSV errors and how to resolve extended passive mode problems.
FTP timeout during transfer — Why FTP transfers timeout and how to fix idle timeout or firewall issues.