Setting up an Android device as file server I have a spare Android device which I always leave at home. I wonder if i can use it as a file server using its mobile hotspot because I don't have a router and internet at home. Friends always come and always ask to share a few MP3s. I'd like them to browse my Android server at their own leisure without deleting anything.

I have servers ultimate installed, but it always requires to be connected via router or Wi-Fi. Can't seem to find the option so that it will not require an active net connection.
Sure you can, you just need a samba server implementation on your android device (just like the PC)

Here is a full port of Linux Samba server which is very powerful: Sambadroid

This application allows you to share/manage files on your device easily from any device on your network. Simply start your mobile hotspot and let the devices connect.

Then start sambadroid, a good android file explorer can easily retrive the shares eg ES explorer, you can navigate to LAN>>Servers>>Scan and you should see a server called SambaDroid (unless you customized the name)