http transporter

[yifan-gu]

@fengjingchao
I think we actually need a http transporter layer instead of tcp, because:
1, The message is not a stream, it's a packet (like UDP).
2, We want to have reliable transporter layer (TCP could provide that).

So, we actually need http... Otherwise we have to parse TCP stream and (un)packeting each message, which is tedious.