code: func (s *Server) handleKeepAlive(req *ssh.Request) {
  	log.Debugf("Received %q: WantReply: %v", req.Type, req.WantReply)
  
  	// only reply if the sender actually wants a response
  	if req.WantReply {
  		err := req.Reply(true, nil)
  		if err != nil {
  			log.Warnf("Unable to reply to %q request: %v", req.Type, err)
  			return
  		}
  	}
  
  	log.Debugf("Replied to %q", req.Type)
  }
docs: // handleKeepAlive accepts and replies to keepalive@openssh.com requests.