BOOST.CloudPrinter

A cloud printing client application that subscribes to an MQTT topic for print jobs and routes them to local system printers. It bridges remote/cloud print requests to physical printers, supporting multiple document formats.

Architecture

MQTT Broker
    ↓ (subscribe to topic)
Main.java (MqttCallback)
    ↓ (parse JSON message)
PrinterUtils
    ↓ (route by MIME type)
┌───────┬───────┬──────┬──────┐
│  PDF  │  ZPL  │ Text │ Image│
└───┬───┴───┬───┴──┬───┴──┬───┘
    ↓       ↓      ↓      ↓
  javax.print API / TCP Socket (port 9100)
    ↓
Local Printer

Prerequisites

• Java 8+
• MQTT Broker connectivity
• Local printers accessible via Java Print Service
• For ZPL label printers: network access to printer on port 9100

Configuration

config.properties

broker_uri=tcp://p-s01-mqtt-01.westbahr.net:1883
username=nimpos
password=****
printer_topic=label/danieln

Property	Description
broker_uri	MQTT broker connection URI
username	MQTT authentication username
password	MQTT authentication password
printer_topic	MQTT topic to subscribe to for print jobs

Message Format

Incoming MQTT Message (JSON)

{
  "printername": "HP_LaserJet_Pro",
  "base64data": "JVBERi0xLjQK...",
  "type": "application/pdf"
}

Field	Description
printername	Name of the target printer (as registered in the OS)
base64data	Base64-encoded file content
type	MIME type determining the print handler

Supported MIME Types

MIME Type	Handler	Description
application/pdf	printPDF()	PDF documents via PDFBox + javax.print
application/zpl	printZPL()	Zebra label printer format via TCP socket
text/plain	printText()	Plain text via javax.print
image/png	printImage()	PNG images via javax.print
image/jpg	printImage()	JPEG images via javax.print
image/gif	printImage()	GIF images via javax.print

Print Processing

1. MQTT message arrives on the subscribed topic
2. JSON payload is parsed to extract printer name, data, and type
3. Base64 data is decoded to bytes
4. MIME type is matched to the appropriate print handler
5. Printer is resolved by name from the system's available printers
6. Document is sent to the printer

ZPL (Label Printers)

ZPL jobs are sent directly via TCP socket to port 9100 on the printer, bypassing the Java Print Service. Supports feed-and-cut commands for label printers.

Debug Mode

Run with --debug or -d flag to write decoded files to disk instead of printing:

java -jar Printer.jar --debug

Status Indicators

The application displays a small UI window with:

• Green checkmark — connected and operational
• Red X — error or connection lost (auto-reconnects)

Dependencies

Dependency	Version	Purpose
paho.mqttv3	1.0.2	MQTT client
pdfbox	2.0.7	PDF rendering for print
batik-*	1.7	SVG status display

Running

java -jar Printer.jar

The application connects to the MQTT broker, subscribes to the configured topic, and waits for print jobs. It auto-reconnects on connection loss.