MQTT Broker disconnection/ unresponsive

[Ricky-001]

During one of my personal projects, I noticed that the MQTT Broker is refusing more than 4 or 5 connections (NOT simultaneous). As a result, the broker remains unresponsive to any new clients or publish transactions after this limit.

So I have this MQTT publish code (PubSubClient) on an ESP32 running in deep-sleep mode - on every trigger, the ESP32 (client) connects to the broker (an ESP8266), publishes a message, and disconnects - going back to sleep. I have another client on my Andriod device, subscribed to this broker, listening for the messages. In this setup, the broker refuses new connections or messages after the publishing client (ESP32) has published 4 messages, and the client fails to connect with status -4.

However, when I reset the ESP8266 either manually or programmatically, it is ready to accept new messages again. Is this expected? I wasn't able to determine, but are the resources not being freed up when clients are disconnecting? Is there anything wrong that I'm doing?

• Here is my ESP32 MQTT Client Code.
• This is the ESP8266 MQTT Broker Code (of course taken from HERE)