Mosquitto MQTT Broker：连接外部代理、订阅主题及断连重连脚本实现问询

Hey there! Let's break down your two Mosquitto needs step by step—super straightforward once you know the tricks.

1. Connecting Your Local Mosquitto Broker to an External Proxy & Subscribing to External Topics #

To pull in topics from an external MQTT broker, you'll want to set up a Mosquitto bridge—this lets your local broker mirror topics from the external one (or even sync both ways). Here's how to do it:

• First, open your Mosquitto config directory (usually /etc/mosquitto/conf.d/) and create a new bridge config file, like external-bridge.conf.
• Add these lines (replace the placeholders with your external broker's details):

  connection external-proxy-bridge
  address external-broker-host:1883  # Replace with actual host:port
  # Uncomment these if the external broker requires auth
  # remote_username your-external-username
  # remote_password your-external-password
  # Define topic bridging: format is <local-topic> <remote-topic> <direction>
  # Use "in" to pull external messages to local, "out" to send local to external, "both" for bidirectional
  topic # in  # This subscribes to ALL external topics and forwards them to your local broker
  # Or use a specific topic if you don't need everything:
  # topic my/local/topic in my/external/topic
  

• Save the file, then restart Mosquitto to apply the changes:

  sudo systemctl restart mosquitto
  

• Once the bridge is up, you can subscribe to the mirrored topics on your local broker just like you normally would. For example, if you used the # in rule, running mosquitto_sub -V mqttv311 -t "#" on your local machine will show all messages from the external broker.

2. Bash Script to Monitor Subscription & Auto-Reconnect #

While mosquitto_sub has basic reconnection logic, a custom script gives you more control over monitoring and restarting. Here's a robust bash script that will keep your subscription alive:

#!/bin/bash

# --- CONFIGURATION ---
MQTT_BROKER="localhost"
MQTT_TOPIC="your-target-topic"  # Replace with your actual topic
MQTT_VERSION="mqttv311"
EXTRA_FLAGS=""  # Add flags like "-u your-user -P your-pass" if needed
CHECK_INTERVAL=5  # Seconds between connection checks
LOG_FILE="/var/log/mqtt_sub_monitor.log"  # Optional: log to a file
# ---------------------

start_sub() {
    echo "$(date): Starting subscription to $MQTT_TOPIC on $MQTT_BROKER..." | tee -a $LOG_FILE
    # Launch the subscription in the background, redirect output to log
    mosquitto_sub -V $MQTT_VERSION -h $MQTT_BROKER -t $MQTT_TOPIC $EXTRA_FLAGS >> $LOG_FILE 2>&1 &
    SUB_PID=$!
    echo "$(date): Subscription started with PID $SUB_PID" | tee -a $LOG_FILE
}

# Start the subscription initially
start_sub

# Monitoring loop
while true; do
    # Check if the subscription process is still running
    if ! kill -0 $SUB_PID 2>/dev/null; then
        echo "$(date): Subscription lost! Restarting..." | tee -a $LOG_FILE
        start_sub
    fi
    sleep $CHECK_INTERVAL
done

How to use this script: #

1. Replace the configuration values with your own (broker address, topic, auth flags if needed).
2. Make the script executable:

   chmod +x mqtt_auto_reconnect.sh
   

3. Run it in the background so it keeps working even if you log out:

   nohup ./mqtt_auto_reconnect.sh &
   

4. For even better persistence, you can set it up as a systemd service—this way it starts automatically on boot and restarts if your server reboots.

Extra tips: #

• The LOG_FILE line lets you track when the subscription starts/restarts—super helpful for debugging.
• Adjust CHECK_INTERVAL to make the checks more or less frequent (5 seconds is a good middle ground).

内容的提问来源于stack exchange，提问作者2437850