SFTP Can't upload module despite using owner's credentials
Using ssh you can log in to the system to check about directory permissions using the same credentials you use with sftp.  

try..  

ssh user@host


to login and then use a number of commands to check permissions

ls -l                      //Lists files with permissions for user, group and other
chmod 755 dir/file         //Change file/directory permission
chown user:group dir/file  //Change the user/group ownership of file(s)


scp command can also upload file from local (*nix) machine to server.

scp path/to/local/file user@host:/path/on/server