魔术字：9位，当前值为“EventMesh”

通信协议版本号：4位，当前值为“0000”

消息总长度值(length)：4位，int类型

消息头长度值(headerLength)：4位，int类型

消息头(header)：长度 = headerLength

消息体(body)：长度 = length - headerLength - 4 - 4  

public class Package {

    private Header header;
    private Object body;
}


public class Header {

    private Command cmd;
    private int code;
    private String msg;
    private String seq;
}

public enum Command {

    //心跳
    HEARTBEAT_REQUEST(0),                              //client发给server的心跳包
    HEARTBEAT_RESPONSE(1),                             //server回复client的心跳包

    //握手
    HELLO_REQUEST(2),                                  //client发给server的握手请求
    HELLO_RESPONSE(3),                                 //server回复client的握手请求

    //断连
    CLIENT_GOODBYE_REQUEST(4),                         //client主动断连时通知server
    CLIENT_GOODBYE_RESPONSE(5),                        //server回复client的主动断连通知
    SERVER_GOODBYE_REQUEST(6),                         //server主动断连时通知client
    SERVER_GOODBYE_RESPONSE(7),                        //client回复server的主动断连通知

    //订阅管理
    SUBSCRIBE_REQUEST(8),                              //client发给server的订阅请求
    SUBSCRIBE_RESPONSE(9),                             //server回复client的订阅请求
    UNSUBSCRIBE_REQUEST(10),                           //client发给server的取消订阅请求
    UNSUBSCRIBE_RESPONSE(11),                          //server回复client的取消订阅请求

    //监听
    LISTEN_REQUEST(12),                            	   //client发给server的启动监听请求
    LISTEN_RESPONSE(13),                               //server回复client的监听请求

    //RR
    REQUEST_TO_SERVER(14),                             //client将RR请求发送给server
    REQUEST_TO_CLIENT(15),                             //server将RR请求推送给client
    REQUEST_TO_CLIENT_ACK(16),                         //client收到RR请求后ACK给server
    RESPONSE_TO_SERVER(17),                            //client将RR回包发送给server
    RESPONSE_TO_CLIENT(18),                            //server将RR回包推送给client
    RESPONSE_TO_CLIENT_ACK(19),                        //client收到回包后ACK给server

    //异步事件
    ASYNC_MESSAGE_TO_SERVER(20),                       //client将异步事件发送给server
    ASYNC_MESSAGE_TO_SERVER_ACK(21),                   //server收到异步事件后ACK给client
    ASYNC_MESSAGE_TO_CLIENT(22),                       //server将异步事件推送给client
    ASYNC_MESSAGE_TO_CLIENT_ACK(23),                   //client收到异步事件后ACK给server

    //广播
    BROADCAST_MESSAGE_TO_SERVER(24),                   //client将广播消息发送给server
    BROADCAST_MESSAGE_TO_SERVER_ACK(25),               //server收到广播消息后ACK给client
    BROADCAST_MESSAGE_TO_CLIENT(26),                   //server将广播消息推送给client
    BROADCAST_MESSAGE_TO_CLIENT_ACK(27),               //client收到广播消息后ACK给server

    //重定向指令
    REDIRECT_TO_CLIENT(30),                            //server将重定向指令推动给client
}

public class LiteMessage {

    private String bizSeqNo;

    private String uniqueId;

    private String topic;

    private String content;

    private Map<String, String> prop;

    private long createTime = System.currentTimeMillis();
}