Connection time out when try to retrieve directory listing

[Praveen]

It's logged in successfully but 95 % times it's got failed to retrieve directory listing. The problem was not available till version 3.9.0.6.

The log -
Status: Connecting to xxx.xx.xx.xx:21...
Status: Connection established, waiting for welcome message...
Status: Initializing TLS...
Status: Verifying certificate...
Status: TLS connection established.
Status: Server does not support non-ASCII characters.
Status: Connected
Status: Retrieving directory listing of "/public_html"...
Command: CWD /public_html
Response: 250 OK. Current directory is /public_html
Command: TYPE I
Response: 200 TYPE is now 8-bit binary
Command: PASV
Response: 227 Entering Passive Mode (xxx,xx,xx,xx,162,66)
Command: MLSD
Error: Connection timed out after 20 seconds of inactivity
Error: Failed to retrieve directory listing

[Tim Kosse]

Your server advertises explicit FTP over TLS support, yet your server is behind a firewall that is not configured correctly for FTP over TLS. Please contact your server administrator or server hosting provider for assistance so that the server's firewall can get fixed.