Remove extra call to Close

We always close the connection in HandleClient, so calling it in
HandleRequest makes will call it twice. Remove the extra call.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Move header construction to separate file

We're creating the header by concatenating strings. This is a bit error
prone and should be moved to a separate file.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>
Add alternative SendAsync which sends entire array

The SendAsync method requires a byte array and the size of the byte array,
or actually the number of bytes that should be sent. It would however be
better if we just had to specify the byte array for the case where the
entire array should be sent.

Signed-off-by: Marcus Karlsson <mk@acc.umu.se>