client.on('data', function(data) {
    const buf = Buffer.from(data,'utf-8')
    const msgType = buf[3]
    const msgLenBuf = Buffer.from([buf[4],buf[5],buf[6],buf[7]])
    const msgLength = msgLenBuf.readInt32BE(0)
    const msgBuf = Buffer.alloc(msgLength)
    buf. copy(msgBuf,0,8,msgLength + 8);
    switch (msgType){
      case 8:
        console.log("认证成功，开始发送开始同步包")
        sendBegin(msgBuf)
        break;
      default:
        break;
    }
});

/**
 * 发送开始同步包
 * @param msg
 */
function sendBegin(msg) {
  var newObj = JSON.parse(msg.toString()  || '[]')
  if(newObj == null || newObj == undefined)
    return;
  var token = newObj.token
  if(token == null || newObj == undefined)
    return;
  client.write(getBeginMsg(token))
}

/**
 * 生成开始同步包
 * @param data
 */
function getBeginMsg(token) {
  const bufHead = Buffer.from([0,0,1,2]);
  const bufMsg = Buffer.from(token)
  const buflength = Buffer.alloc(4,0)
  buflength.writeIntBE(bufMsg.length, 0, 4);
  const totalLength = bufHead.length + buflength.length + bufMsg.length;
  return Buffer.concat([bufHead,buflength,bufMsg],totalLength);

}