FTPS: Prevent closing of command channel during lengthy operations
In some cases, when the large amount of data is transferred over the data channel and the command channel stays idle, command socket is closed either by the server itself (rarely) or by some intermediate firewall or router.
To prevent such behavior you can use so called keep-alive requests. In FTPS they are done with help of NOOP command, sent over the command channel during the data transfer. TElSimpleFTPSClient.TransferKeepAliveInterval property allows to set the keep alive interval and send NOOP during large file transfers.