Hi,
I know two public SFTP servers which you can connect to. Both of them are read-only.

One is https://test.rebex.net/.

Second is WinFTP Server https://www.wftpserver.com/onlinedemo.htm. Despite its name it serves files over SFTP too.

List of public SFTP servers is maintained at https://www.sftp.net/public-online-sftp-servers

Here is CoreFTP's mini-sftp server for Windows.
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You should not have much trouble locating a Windows machine to run it on. :)
http://www.coreftp.com/server/

-- Kamilion

Hi, does anyone have the details of a functional, publicly accessible SFTP server that can be used for testing my client? I just want a server to try connecting/disconnecting. The reason is that I only have the details of one SFTP server which I am failing to connect to so I want to see if the problem is at the server end or my end. Thanks.

I have found such a site for FTPS (ftp.secureftp-test.com) but not for SFTP.