def connect(host=nil, port=nil, &cb)
      host ||= opts[:upstream_host] || raise('no upstream host')
      port ||= opts[:upstream_port] || raise('no upstream port')
      cb   ||= lambda { |conn| opts[:session_callback].call(self, conn) }
      log.debug "Making upstream connection to #{host}:#{port}"
      EM.connect(host, port, Connection, opts[:upstream_args], &cb)
    end
def connect(host=nil, port=nil, &cb)
      host ||= opts[:upstream_host] || raise('no upstream host')
      port ||= opts[:upstream_port] || raise('no upstream port')
      cb   ||= lambda { |conn| opts[:session_callback].call(self, conn) }
      log.debug "Making upstream connection to #{host}:#{port}"
      EM.connect(host, port, Connection, opts[:upstream_args], &cb)
    end
Used by filters to initiate upstream connection in response to
 inbound connection