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@@ -11,18 +11,43 @@ connections between the client, typically a Web browser,
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and the server. It uses the HTTP Upgrade mechanism to
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establish the connection.
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-Websocket connections are asynchronous, unlike HTTP. This
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-means that not only can the client send frames to the server
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-at any time, but the server can also send frames to the client
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-without the client initiating anything other than the
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-Websocket connection itself. This allows the server to push
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-data to the client directly.
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+Websocket connections are fully asynchronous, unlike
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+HTTP/1.1 (synchronous) and HTTP/2 (asynchronous, but the
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+server can only initiate streams in response to requests).
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+With Websocket, the client and the server can both send
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+frames at any time without any restriction. It is closer
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+to TCP than any of the HTTP protocols.
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Websocket is an IETF standard. Cowboy supports the standard
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and all drafts that were previously implemented by browsers,
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excluding the initial flawed draft sometimes known as
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"version 0".
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+=== Websocket vs HTTP/2
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+
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+For a few years Websocket was the only way to have a
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+bidirectional asynchronous connection with the server.
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+This changed when HTTP/2 was introduced. While HTTP/2
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+requires the client to first perform a request before
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+the server can push data, this is only a minor restriction
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+as the client can do so just as it connects.
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+
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+Websocket was designed as a kind-of-TCP channel to a
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+server. It only defines the framing and connection
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+management and lets the developer implement a protocol
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+on top of it. For example you could implement IRC over
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+Websocket and use a Javascript IRC client to speak to
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+the server.
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+
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+HTTP/2 on the other hand is just an improvement over
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+the HTTP/1.1 connection and request/response mechanism.
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+It has the same semantics as HTTP/1.1.
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+
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+If all you need is to access an HTTP API, then HTTP/2
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+should be your first choice. On the other hand, if what
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+you need is a different protocol, then you can use
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+Websocket to implement it.
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+
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=== Implementation
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Cowboy implements Websocket as a protocol upgrade. Once the
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@@ -37,7 +62,9 @@ covering all aspects of the protocol. Cowboy passes the
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suite with 100% success, including all optional tests.
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Cowboy's Websocket implementation also includes the
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-x-webkit-deflate-frame compression draft which is being used
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-by some browsers to reduce the size of data being transmitted.
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+permessage-deflate and x-webkit-deflate-frame compression
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+extensions.
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+
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Cowboy will automatically use compression as long as the
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-`compress` protocol option is set when starting the listener.
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+`websocket_compress` protocol option is set when starting
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+the listener.
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Loïc Hoguin