class WebSocket::Driver::Hybi

def handshake_response
  sec_key = @socket.env['HTTP_SEC_WEBSOCKET_KEY']
  version = @socket.env['HTTP_SEC_WEBSOCKET_VERSION']
  unless version == VERSION
    raise ProtocolError.new("Unsupported WebSocket version: #{ VERSION }")
  end
  unless sec_key
    raise ProtocolError.new('Missing handshake request header: Sec-WebSocket-Key')
  end
  @headers['Upgrade']              = 'websocket'
  @headers['Connection']           = 'Upgrade'
  @headers['Sec-WebSocket-Accept'] = Hybi.generate_accept(sec_key)
  @headers['Sec-WebSocket-Protocol'] = @protocol if @protocol
  extensions = @extensions.generate_response(@socket.env['HTTP_SEC_WEBSOCKET_EXTENSIONS'])
  @headers['Sec-WebSocket-Extensions'] = extensions if extensions
  start   = 'HTTP/1.1 101 Switching Protocols'
  headers = [start, @headers.to_s, '']
  headers.join("\r\n")
end