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当我们有 http2 双向流时，为什么我们需要 SSE？

[英]Why do we need SSE when we have http2 bidirectional streaming?

原文 2018-01-19 15:41:30 3 1 http2

This may seem elementary but i didn't find any answers on internet.这可能看起来很简单，但我在互联网上没有找到任何答案。

My understanding of SSE (server sent events) is that data is sent from server to client on a TCP connection when the data is available on the server, if the connection is closed, a new connection is opened by the client.我对SSE （服务器发送事件）的理解是，当服务器上的数据可用时，数据通过TCP连接从服务器发送到客户端，如果连接关闭，客户端会打开一个新连接。

In http2 bidirectional streaming we are streaming the data from server when it is available and connection is kept open.在http2双向流中，我们在服务器可用且连接保持打开时从服务器流式传输数据。 This does the same as SSE .这与SSE相同。

I am not referring to http2 server push.我不是指http2服务器推送。

1 个解决方案

In an HTTP/2 connection, you have individual streams.在 HTTP/2 连接中，您有单独的流。 Those streams (except for the push promises) need to get opened by the client to send a HTTP request, then the server can send an answer.这些流（推送承诺除外）需要由客户端打开以发送 HTTP 请求，然后服务器可以发送答案。

So you still need a stream to be opened by a client, waiting for the server to send some data.所以你仍然需要一个 stream 被客户端打开，等待服务器发送一些数据。

And then the whole connection might break down (just like a HTTP/1.1 connection, or a plain TCP one), which means the client still needs to open a new connection (and open a stream there).然后整个连接可能会中断（就像一个 HTTP/1.1 连接，或者一个普通的 TCP 连接），这意味着客户端仍然需要打开一个新连接（并在那里打开一个 stream）。

So HTTP/2 doesn't solve anything here which would make SSE superfluous.所以 HTTP/2 在这里没有解决任何会使 SSE 变得多余的问题。

As mentioned by Yami Odymel in a comment, the SSE specification also specifies the exact format of the messages being sent.正如 Yami Odymel 在评论中提到的，SSE 规范还指定了发送消息的确切格式。