[bug] Sec-WebSocket-Key header accepting longer values than RFC6455 accepts. #617

I sent a 20 byte value as Sec-WebSocket-Key and everything works fine, but the RFC states that the value must be exactly 16 bytes when decoded from base64!

That's a problem because when I try to use the client I am writing and testing against this websocket server, it fails on another websocket server.

I'm letting you know so we can all follow the RFC.

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