About void[] and asockets

[Jolly James via Digitalmars-d-learn]

For sure, some might know ae. I am trying to use it as TcpServer. 
I got almost everything working fine concerning connection 
establishment and disconnecting. But there is one thing that 
makes it hard for me to understand, how to handle data.

https://github.com/CyberShadow/ae/blob/master/net/asockets.d

Well, what are these void-arrays for real? I mean, they contain 
data what does not make them really void, does it?

And how to I get received data out of Data.content[]?
How to use TcpConnection.send()? E.g. for sending a string?