char xml_body[4096];是什么意思

问题遇到的现象和发生背景

char xml_body[4096];是什么意思，gb28181里面碰到

问题相关代码，请勿粘贴截图

static void st_gb28181_keepAlive(struct eXosip_t *context)        //保持活力函数
{
    osip_message_t *rqt_msg = NULL;        //SIP消息的结构(请求和响应)指针
    char to[100];        /*sip:主叫用户名@被叫IP地址*/
    char from[100];        /*sip:被叫IP地址:被叫IP端口*/
    char xml_body[4096];
    memset(to, 0, 100);
    memset(from, 0, 100);
    memset(xml_body, 0, 4096);
    snprintf(to,sizeof(to), "sip:%s@%s:%s", gb28181_device_info.server_id,gb28181_device_info.server_ip, gb28181_device_info.server_port);
    snprintf(from,sizeof(from), "sip:%s@%s:%s", gb28181_device_info.ipc_id, gb28181_device_info.server_ip,gb28181_device_info.server_port);
    eXosip_message_build_request(context,&rqt_msg, "MESSAGE", to, from, NULL);/*构建"MESSAGE"请求*/
    snprintf(xml_body, 4096, "\n"
        "\n"
        "Keepalive\n"/*命令类型*/
        "1\n"/*命令序列号*/
        "%s\n"/*设备编码*/
        "OK\n"/*是否正常工作*/
        "\n",
        gb28181_device_info.ipc_id);
    osip_message_set_body(rqt_msg, xml_body, strlen(xml_body));
    osip_message_set_content_type(rqt_msg, "Application/MANSCDP+xml");
    eXosip_lock(context);
    eXosip_message_send_request(context,rqt_msg);/*回复"MESSAGE"请求*/
    eXosip_unlock(context);
    dbg("dt_eXosip_sendKeepAlive success!\n");
}

char xml_body[4096]
xml的文件内容吧

char xml_body[4096];/* 开辟一个char的xml_body缓冲区空间；用来存储数据传输过程中的xml内容 */