http 协议是基于TCP还是UDP

虽然不限于TCP，但基本可以认为是基于 TCP，不能使用UDP。

参考：

http://www.w3.org/Protocols/rfc2616/rfc2616.txt

   HTTP communication usually takes place over TCP/IP connections. The   default port is TCP 80 [19], but other ports can be used. This does   not preclude HTTP from being implemented on top of any other protocol   on the Internet, or on other networks. HTTP only presumes a reliable   transport; any protocol that provides such guarantees can be used;   the mapping of the HTTP/1.1 request and response structures onto the   transport data units of the protocol in question is outside the scope   of this specification.