what does message passing mean ? http or udp

Hoi,

we use message in distributed system, what does message means?开发者_运维知识库

we can say UDP use message but not HTTP,can anybody tell me the reason ?

Thanks a lot

Message is a piece of information you pass around :)

UDP is faster, simpler and has no guarantees of order of delivery and even the very delivery of messages (packets). HTTP rides on TCP, which guarantees delivery in order, with necessary retries, etc, but it has a bit more overhead, and HTTP adds even more to the overhead.