Hi,
I have a connection setup to download files from a SFTP (SSH - Secure Shell) server using a public key as authorisation.
I can access this server using the ftp explorer and download files from it.
I use this connection for a remote file trigger. All trigger settings are default except I cheked the Created file checkbox to watch for new files.
Overnight the job downloaded several files, but than the trigger was inactivated. Looking at the log_server file I saw a lot of trigger errors:
1/5/2018 1:55:57 AM	Err	Connect->Error connecting: Object reference not set to an instance of an object. (SFTP (SSH - Secure Shell) - connectionname [username@ipnumber])
1/5/2018 1:55:57 AM	Err	UpdateFileListing->Error in Trigger: 'nieuwe file gevonden op de FTP', ex: System.NullReferenceException: Object reference not set to an instance of an object.
   at VisualCronService.RemoteFileAPI.GetRemoteFileList(String strConnectionId, RemoteFileFilterClass rff, VariableReplacerClass VR, ConnectionHandlerClass chIn)
   at OBOKIIHBDBPMCFALPGECCIFHCDJPEDKODDGK.PJMGPNGGFJGPLJFPIKKEHCDNMAGACLNIEOEN.HPFDFOEFEHIIPICGDDKMELIDHKACPECLEJHG(Boolean  )
I see also normal download behaviour:
1/5/2018 3:36:58 AM	Info	RemoteFileTrigger->DownloadFile: /20180105_033401_M_D_00007.csv to 
1/5/2018 3:36:58 AM	Info	Job started: jobname
1/5/2018 3:36:58 AM	Info	Task started(FTP/FTPS/SFTP/SCP): Download de gevonden file (26941335)
1/5/2018 3:36:59 AM	Info	Task completed (Success)->'Download de gevonden file' (26941335)
1/5/2018 3:36:59 AM	Info	Task started(Email): Email (26941336)
1/5/2018 3:36:59 AM	Info	Task completed (Success)->'Email' (26941336)
1/5/2018 3:37:00 AM	Info	Job completed (Success)->'jobname'
one other error:
1/5/2018 6:29:00 AM	Err	Connect->Error connecting: Connection error 10061 (SFTP (SSH - Secure Shell) - connectionname [username@ipnumber])
1/5/2018 6:29:00 AM	Err	UpdateFileListing->Error in Trigger: 'nieuwe file gevonden op de FTP', ex: SBSftpCommon.EElSFTPError: SFTP component not connected
   at SBSftp.TElSftpClient.RequestAbsolutePathSync(String Path)
   at SBSimpleSftp.TElSimpleSFTPClient.RequestAbsolutePath(String Path)
   at VisualCronService.RemoteFileAPI.GetRemoteFileList(String strConnectionId, RemoteFileFilterClass rff, VariableReplacerClass VR, ConnectionHandlerClass chIn)
   at OBOKIIHBDBPMCFALPGECCIFHCDJPEDKODDGK.PJMGPNGGFJGPLJFPIKKEHCDNMAGACLNIEOEN.HPFDFOEFEHIIPICGDDKMELIDHKACPECLEJHG(Boolean  )
This last error repeats itself every 5-6 seconds and after a while I see:
1/5/2018 6:33:09 AM	Err	Unhandled exception occured in Remote file Trigger: SFTP component not connected
1/5/2018 6:33:09 AM	Err	Trigger error: SFTP component not connected
1/5/2018 6:33:09 AM	Debug	Trigger was expired and inactivated
To my knowledge the server was up all night. 
What is happening here?
Regards,
Erik
                            
Uses Visualcron since 2006.