Ssh server. File transfers with protocol SCP and SFTP are available. Command line is also available (beta version). Command line needs "/system/bin/sh" preinstalled.
To start the server automatically use application "Autostart and StaY!"
or also Tasker with the intents provided.
I have tested the server using:
*Secure file transfer:
WinSCP : http://winscp.net/
FileZilla : https://filezilla-project.org/
Putty : http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html