Getting an "unable to find a valid port" error after multiple file downloads. Then, you need to restart the server when this error comes up.

Ports are not getting freed up after multiple file downloads. I need to restart the server after getting this error. It works for some time, but after multiple file downloads, it gives this error again.

`Response:`    400 Unable to find valid port
Command:    PORT `49,36,51,124,206,82`

