I'm FTPing to several locations. They all work except one. They all
worked before I installed ZFTP server at all the locations.

For this one location it hangs for about 15 seconds and then displays
white screen when it reaches this line of code.

$conn_id = ftp_connect($ftp_server);

I've looked at this a hundred times. The IP is correct. I can FTP to
this location with any number of FTP programs so the server appears to
be working correctly. There is nothing in the error log on my site.

What am I missing?