Quote RFC 2616 (HTTP/1.1): "HTTP communication usually takes place over TCP/IP connections. The default port is TCP 80 [19], but other ports can be used. This

Quote RFC 2616 (HTTP/1.1): "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." So while it doesn't rule out protocols other than TCP, it does exclude UDP.