FTPSClient fails to connect with MalformedServerReplyException-CodePudding

I'm using the following code:

val ftpClient = FTPSClient()
ftpClient.connect(host, port)

And getting the following error:

org.apache.commons.net.MalformedServerReplyException: Could not parse response code.
Server Reply: SSH-2.0-BIS FileExchange Gateway 2.70.1

It's as if the client is not even speaking SSL when it connects but I'm stumped.

Attempt to "coerce" SSL sockets produce no difference:

val sslContext = SSLContext.getInstance("SSL").apply {
    init(null, arrayOf<TrustManager>(TrustManagerUtils.getAcceptAllTrustManager()), null)
}
val ftpClient = FTPSClient(sslContext)
ftpClient.connect(host, port)

Setting the socket factory produced a socket closed exception:

ftpClient.setSocketFactory(sslContext.socketFactory)

I should note that I can operate the endpoint using sftp so I can infer that the endpoint works correctly.

CodePudding user response：

FTPSClient implements FTPS, i.e. FTP over SSL/TLS. It is expected that you connect to an FTP server with TLS support. The error message indicates though that you connect to a SSH server, not a FTP server. This means that you are probably trying to use SFTP (file transfer over SSH) not FTPS. Thus, there is a mismatch in the protocol spoken between client and server.

For how to use SFTP instead of FTPS see for example How to retrieve a file from a server via SFTP?.

CodePudding user response：

This finally worked for me and some of it may have to do with the way the endpoint is configured but I'm not sure.

ftpClient.connect(host)
// This is very important!
ftpClient.execPROT("P")
ftpClient.login(username, password)
// This is very important!
ftpClient.enterLocalPassiveMode()