Thanks. I'll look into this certificate chain. The FTPS uses explicit encryption, hence it should be technically possible to connect to the server.
The error after the logging I posted earlier is this:
Catching java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:368)
at java.net.Socket.connect(Socket.java:531)
at java.net.Socket.connect(Socket.java:477)
at java.net.Socket.<init>(Socket.java:374)
at java.net.Socket.<init>(Socket.java:187)
at iaik.security.ssl.SSLSocket.<init>(Unknown Source)
at com.sap.aii.security.lib.net.ssl.impl.IAIKSSLSocketFactoryImpl$SSLDebugSocketImpl.<init>(IAIKSSLSocketFactoryImpl.java:266)
at com.sap.aii.security.lib.net.ssl.impl.IAIKSSLSocketFactoryImpl.createSocket(IAIKSSLSocketFactoryImpl.java:144)
at com.sap.aii.adapter.file.ftp.FTPCtrl.createDataSocketPASV(FTPCtrl.java:437)
at com.sap.aii.adapter.file.ftp.FTPCtrl.createDataSocket(FTPCtrl.java:290)
at com.sap.aii.adapter.file.ftp.FTPCl.dir(FTPCl.java:1125)
at com.sap.aii.adapter.file.ftp.FTPCl.listFiles(FTPCl.java:1230)
at com.sap.aii.adapter.file.File2XI.getFtpList(File2XI.java:850)
at com.sap.aii.adapter.file.File2XI.invoke(File2XI.java:637)
at com.sap.aii.af.lib.scheduler.JobBroker$Worker.run(JobBroker.java:534)
at com.sap.engine.core.thread.impl3.ActionObject.run(ActionObject.java:37)
at java.security.AccessController.doPrivileged(Native Method)
at com.sap.engine.core.thread.impl3.SingleThread.execute(SingleThread.java:182)
at com.sap.engine.core.thread.impl3.SingleThread.run(SingleThread.java:280)