The File Transfer (FTP) monitor works by connecting to an FTP service and checking to see that it is responding. There are no settings necessary for this monitor.
The File Transfer (FTP) monitor first initiates a connection to the service and waits for a "220" response. It then sends a "NOOP" command to the service and waits for a "200" response. (This "non-operation" does nothing, but ensures that the service is responding to commands.)
Note that some FTP server applications send a "530 User not logged in" response to the "NOOP" command. Even though this officially an error, in this case it still indicates that the service is responding properly.
The monitor then sends a "QUIT" command, and waits for a "221" response to indicate that it was disconnected from the service.
If the monitor receives the "221" response, the test is successful.
If the monitor receives an error response (usually a "4xx" or "5xx" response code) at any step of the check, the test will fail with an error.
If the monitor does not receive the expected response at any step of the check, it will continue to wait for the desired response before continuing to the next step. If the desired response is never received, the test will fail with a timeout error.