Are you sure that you added the right IP to the whitelist file? You also have to wait up to 10 minutes after changing the whitelist, because the TS3 server only reloads changes of this file every 5 or 10 minutes (will be displayed in the server log). Of course you can also restart the TS3 server process (like TotoIsBack wrote).
If only 127.0.0.1 is on the whitelist, the bot also have to use 127.0.0.1 to connect to the TS3 server. If you use the IP address of the real network card, you have to add this IP to the TS3 server query whitelist file.
Using screen is just one way to start a background application on linux. If you want to use this, make sure that screen is installed. It deepens on the linux distribution how to install screen. The Debian way (which also works on Ubuntu and PC Linux OS) to install screen is written into my readme.txt file (using apt-get).