Sysax Product Forums / Sysax Multi Server / Bugs and Feature Requests / Clients unable to connect
Posted:  26 Oct 2009 18:31
Using version 5.1, standard license, configured to listen for FTP/FTPS on port 21.

I'm able to successfully connect from a separate dial-up connection using either protocol. However, I have a number of customers who are not able to connect using either protocol, using a number of FTP clients.

When using FTPS, they will get as far as attempting to open a data connection, but this fails and they are unable to list the contents of their home folder or transfer any files. When using FTP, they are able to log in but the connection will hang when trying to list folder contents or transferring files. This happens when using a dedicated FTP client or the Windows FTP command.

On my firewall I have opened port 21, as well as port range 10001 through 10010. This range is configured in the Sysax software. What's wrong?
Posted:  26 Oct 2009 19:33
Hi Jason,

Are these issues happening when the client is using pasv mode or port mode? When you verified the connections, did you use pasv mode or port mode in the client software? Were you able to login correctly using the windows ftp command?

File Transfer Protocol Solutions simplified
Posted:  26 Oct 2009 19:43
In PASV mode, they are unable to connect the data channel. The clients all seem to switch to PORT mode after this fails, and are unable to view folder contents (using LIST).

When I verified, I had PASV mode enabled in my FTP client. When I connect using the Windows FTP command, I am not able to view folder contents. I receive a response of 150 File Status okay; about to open data connection and then the connection hangs.

Here is a sample connection log:

220- Sysax Multi Server Service (Version 5)
234 AUTH command accepted. Setting up SSL/TLS connection
SSL session NOT set for reuse
SSL Session Started.
Host type (1): AUTO
USER Username
331 User name okay, need password
PASS (hidden)
230 User logged in, proceed
215 Windows_NT
Host type (2): Microsoft NT
200 PBSZ Command accepted. Protection buffer set to 0
200 PROT Command accepted
257 "/" is current path
TYPE A200 Command okay
227 Entering Passive Mode (IP address,39,19)
connecting data channel to IP address:39,19(10003)
Failed to connect data channel to IP address:39,19(10003)
PORT 10,255,5,250,236,227
200 Command okay
150 File status okay; about to open data connection

At this point, the connection fails and the user is shown as disconnected in the Sysax log.
Posted:  27 Oct 2009 00:36
What FTP Client are you using to connect? Also, what program are you referring to when you said "connect using the Windows FTP command"? I don't think the ftp.exe program that ships with windows supports secure FTPS. Our developers would like to be able to reproduce this.

SFTP Server Solutions Simplified
Posted:  29 Jan 2010 20:08
This is a common problem with FTPS and sometimes FTP.
When the client requests a directory list or a file download, the server tells the client what port it is going to use. But the Firewall or Router doesnt know, because the traffic is encrypted. So then the firewall blocks the return data from the server and the client times out.

Try using SFTP instead. It is much more firewall friendly.

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