public final class NIOHTTPClientUpgradeHandler : ChannelDuplexHandler, RemovableChannelHandler

A client-side channel handler that sends a HTTP upgrade handshake request to perform a HTTP-upgrade. When the first HTTP request is sent, this handler will add all appropriate headers to perform an upgrade to the a protocol. It may add headers for a set of protocols in preference order. If the upgrade fails (i.e. response is not 101 Switching Protocols), this handler simply removes itself from the pipeline. If the upgrade is successful, it upgrades the pipeline to the new protocol.

The request sends an order of preference to request which protocol it would like to use for the upgrade. It will only upgrade to the protocol that is returned first in the list and does not currently have the capability to upgrade to multiple simultaneous layered protocols.