Ubuntu – uget with aria2 plugin

I have read that uget with aria2 plugin enabled is the best downloader. So I tried.

I downloaded uget from the Ubuntu Software Center and also installed aria2 from the terminal.

Then I opened uget and opened Settings > Plugin section and activated "Enable aria2 plugin". My arguments read: --enable-rpc=true -D --check-certificate=false

Then when I clicked OK, it replied:

Failed to connect to aria2.

Is aria2 shutdown? Or did the aria2 launch fail?

I also tried some commands from web:

roshan@roshan-Aspire-4736Z:~$ aria2c --enable-rpc=true --check-certificate=false --disable-ipv6

2013-09-07 09:42:08.483317 ERROR - IPv4 RPC: failed to bind port 6800
Exception: [SocketCore.cc:308] errorCode=1 Failed to bind a socket, cause: Address already in use

2013-09-07 09:42:08.483629 ERROR - Exception caught
Exception: [DownloadEngineFactory.cc:181] errorCode=1 Failed to setup RPC server

Then I opened YouTube and tried to download a video. It won't download and at the bottom there was this message:

Message: aria2.getVersion result error

Please help me with this. I really need t have Aria2 plugin working.
Thank you.