![nanomq_log](https://github.com/nanomq/nanomq/assets/9456870/4fceffb6-a518-4ea0-9dd1-f4fc6a38a471)

version 0.21.8

nanomq broker 报mqtt broker_tls.c:488: NULL msg detected in send_cb后
客户端连接就会pub不上来消息，重新断开连接进行重连后又恢复，这个是什么原因。
send_cb是什么消息

mqtt broker_tls.c:488: NULL msg detected in send_cb
This is a GitHub Issue
repo:nanomq
owner:emqx
Title : mqtt broker_tls.c:488: NULL msg detected in send_cb
Issue date:

--- start body ---
![nanomq_log](https://github.com/nanomq/nanomq/assets/9456870/4fceffb6-a518-4ea0-9dd1-f4fc6a38a471)

version 0.21.8

nanomq broker 报mqtt broker_tls.c:488: NULL msg detected in send_cb后
客户端连接就会pub不上来消息，重新断开连接进行重连后又恢复，这个是什么原因。
send_cb是什么消息

--- end body ---

The issue indicates a potential problem in the nanomq broker where a NULL message is detected in the send callback function (send_cb). This could lead to a failure in publishing messages when clients are connected, which may indicate a bug in the message handling logic. However, it does not explicitly indicate a security vulnerability, but rather a functional issue that affects message delivery.