bind-local-data-port NcFTPd file configuration
Don't forget to restart NcFTPd after modifying the file.

Setting bind-local-data-port to no causes the server to not bind its end of the (active FTP) data connection to port 20.  This option isn't too useful unless you're debugging the software.

This option is also useful during load-testing where NcFTPd might be communicating with large numbers of connections from a small pool of IP addresses. A TCP connection consists of a server IP address, server port number, client IP address, and client port number. If data connections always originate from port 20 on the server as the RFC for FTP mandates, then connections from a particular client machine will have the same server IP, server port, and client IP, with only the client port remaining as a way to distinguish TCP connections. Therefore, large numbers of connections from the same client machine to the FTP server can easily exhaust the number of possible unique connections resulting in "Address in use" errors.

So, if you're doing load testing, you can enable this option so that the server port is also a variable, rather than being set to port 20. This will greatly increase the number of possible connections from the server to a particular client machine. Since FTP client programs generally don't care about what port the server's data connections originate from, you can enable this for testing.


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