Error "550 SSL/TLS required on the data channel" when connecting to an FTPS server

Symptom

When executing a process which connects to an FTPS server, the following error is raised:

    com.indy.engine.common.exceptions.EngineExceptionI: 550 SSL/TLS required on the data channel
    at com.indy.engine.actionCodes.FtpPutActionCodeI.executeSimpleCode(SourceFile:394)
    at com.indy.engine.action.common.ActionCodeTypeI.executeCode(SourceFile:1608)
    at com.indy.engine.action.common.ActionCodeTypeI.run(SourceFile:1767)
    at java.lang.Thread.run(Unknown Source)

 

Solution

This error message is raised by the FTPS server, because it expects encryption of the data channel.

See RFC2228 for more information.

The solution is to enable the FTP_ENCRYPT_CHANNEL_DATA parameter on the FTP action.