1. When you type "ftp somewhere.com", you are using an FTP "client".
2. Every platform has an ftp client. Usually many of 'em. Most web browsers are even acceptable ftp clients (at least to download files, if not also uploading).
... however ...
3. When you type "ftp somewhere.com", you are trying to reach an FTP "server".
4. And not every platform has a running FTP server.
In fact, most hosts will NOT have an FTP server by default. You generally have to configure and enable an FTP server.
Which, hopefully, explains why you can probably connect in one direction, but not the other. My guess is that both sides have an FTP client, but only one side (your Solaris server) happens to have an operational FTP server.
If you want to add FTP services to Linux, all you usually have to do is run "sudo apt-get install vsftp", or the equivalent for your distro.