Clients can optionally send a DISCONNECT packet to signal that they intend to disconnect. However there is no equivalent for the server. So if a server drops th

Clients can optionally send a DISCONNECT packet to signal that they intend to disconnect. However there is no equivalent for the server. So if a server drops the connection, the client will only find out when it sends its next PING or other packet. Edit: Also, it's worth noting that MQTT 5 greatly expands on the error reasons that the server can send to the client if it wants to indicate precisely why it's dropping the client.