Initial commit: Brother QL USB-to-Network Bridge
- TCP server exposing USB Brother QL printers on port 9100 - Supports all Brother QL series label printers - Async architecture for handling concurrent print jobs - Raspberry Pi deployment script and systemd service - Documentation for setup and InvenTree integration
This commit is contained in:
timmyhadwen
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bridge.py
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261
bridge.py
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#!/usr/bin/env python3
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"""
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Brother QL Bridge - USB to Network Bridge
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Exposes a USB-connected Brother QL printer (e.g., QL-570) on the network
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so it can be used with network-based printing tools like InvenTree's Brother plugin.
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"""
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import argparse
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import asyncio
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import logging
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import signal
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import sys
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import usb.core
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import usb.util
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import config
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# Brother printer USB vendor ID
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BROTHER_VENDOR_ID = 0x04F9
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# Known QL printer product IDs
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PRODUCT_IDS = {
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0x2015: "QL-500",
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0x2016: "QL-550",
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0x2027: "QL-560",
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0x2028: "QL-570",
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0x2029: "QL-580N",
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0x201B: "QL-650TD",
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0x2042: "QL-700",
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0x2043: "QL-710W",
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0x2044: "QL-720NW",
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0x209B: "QL-800",
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0x209C: "QL-810W",
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0x209D: "QL-820NWB",
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0x2020: "QL-1050",
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0x202A: "QL-1060N",
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}
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logger = logging.getLogger("brother-ql-bridge")
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class USBPrinter:
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"""Handles USB communication with the Brother QL printer."""
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def __init__(self, device=None):
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self.dev = None
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self.ep_out = None
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self.ep_in = None
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self._lock = asyncio.Lock()
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if device:
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# Parse device string like "usb://0x04f9:0x2028"
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if device.startswith("usb://"):
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parts = device[6:].split(":")
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vendor = int(parts[0], 16)
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product = int(parts[1].split("/")[0], 16)
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self.dev = usb.core.find(idVendor=vendor, idProduct=product)
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else:
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# Auto-detect Brother QL printer
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self.dev = usb.core.find(idVendor=BROTHER_VENDOR_ID)
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if self.dev is None:
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raise RuntimeError("No Brother QL printer found on USB")
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product_name = PRODUCT_IDS.get(self.dev.idProduct, f"Unknown (0x{self.dev.idProduct:04x})")
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logger.info(f"Found printer: {product_name}")
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def connect(self):
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"""Initialize USB connection to the printer."""
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# Detach kernel driver if necessary
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try:
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if self.dev.is_kernel_driver_active(0):
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self.dev.detach_kernel_driver(0)
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logger.debug("Detached kernel driver")
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except (usb.core.USBError, NotImplementedError):
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pass
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# Set configuration
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try:
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self.dev.set_configuration()
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except usb.core.USBError:
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pass # Already configured
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# Get endpoints
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cfg = self.dev.get_active_configuration()
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intf = cfg[(0, 0)]
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self.ep_out = usb.util.find_descriptor(
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intf,
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custom_match=lambda e: usb.util.endpoint_direction(e.bEndpointAddress)
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== usb.util.ENDPOINT_OUT,
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)
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self.ep_in = usb.util.find_descriptor(
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intf,
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custom_match=lambda e: usb.util.endpoint_direction(e.bEndpointAddress)
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== usb.util.ENDPOINT_IN,
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)
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if self.ep_out is None:
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raise RuntimeError("Could not find USB OUT endpoint")
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logger.info("USB connection established")
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def write_sync(self, data: bytes) -> int:
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"""Write data to the printer synchronously with proper timeout."""
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# Write in chunks with longer timeout (15 seconds)
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chunk_size = 32768
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total_written = 0
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for i in range(0, len(data), chunk_size):
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chunk = data[i : i + chunk_size]
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written = self.ep_out.write(chunk, timeout=15000)
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total_written += written
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return total_written
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async def write(self, data: bytes) -> int:
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"""Write data to the printer asynchronously."""
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async with self._lock:
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try:
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return await asyncio.get_event_loop().run_in_executor(
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None, self.write_sync, data
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)
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except usb.core.USBError as e:
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logger.error(f"USB write error: {e}")
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raise
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def close(self):
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"""Release USB resources."""
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if self.dev:
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usb.util.dispose_resources(self.dev)
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class PrinterBridge:
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"""TCP to USB bridge server."""
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def __init__(self, printer: USBPrinter, host: str, port: int):
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self.printer = printer
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self.host = host
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self.port = port
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self.server = None
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self.job_count = 0
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async def handle_client(
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self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter
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):
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"""Handle incoming print job from TCP client."""
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addr = writer.get_extra_info("peername")
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self.job_count += 1
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job_id = self.job_count
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logger.info(f"[Job {job_id}] Connection from {addr}")
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try:
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# Buffer entire job first (Brother raster protocol works best this way)
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chunks = []
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while True:
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data = await reader.read(4096)
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if not data:
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break
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chunks.append(data)
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job_data = b"".join(chunks)
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logger.info(f"[Job {job_id}] Received {len(job_data)} bytes, sending to printer...")
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# Send complete job to printer
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await self.printer.write(job_data)
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logger.info(f"[Job {job_id}] Completed successfully")
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except Exception as e:
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logger.error(f"[Job {job_id}] Error: {e}")
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finally:
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writer.close()
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await writer.wait_closed()
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async def start(self):
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"""Start the bridge server."""
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self.server = await asyncio.start_server(
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self.handle_client, self.host, self.port
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)
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addrs = ", ".join(str(sock.getsockname()) for sock in self.server.sockets)
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logger.info(f"Bridge server listening on {addrs}")
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async with self.server:
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await self.server.serve_forever()
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async def stop(self):
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"""Stop the bridge server."""
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if self.server:
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self.server.close()
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await self.server.wait_closed()
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async def main():
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parser = argparse.ArgumentParser(
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description="Bridge a USB Brother QL printer to the network"
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)
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parser.add_argument(
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"-p", "--port",
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type=int,
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default=config.TCP_PORT,
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help=f"TCP port to listen on (default: {config.TCP_PORT})"
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)
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parser.add_argument(
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"-H", "--host",
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default=config.TCP_HOST,
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help=f"Host/IP to bind to (default: {config.TCP_HOST})"
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)
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parser.add_argument(
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"-d", "--device",
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default=config.USB_DEVICE,
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help="USB device (e.g., usb://0x04f9:0x2028). Auto-detect if not specified"
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)
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parser.add_argument(
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"-v", "--verbose",
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action="store_true",
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help="Enable verbose logging"
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)
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args = parser.parse_args()
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# Setup logging
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log_level = logging.DEBUG if args.verbose else getattr(logging, config.LOG_LEVEL)
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logging.basicConfig(
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level=log_level,
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format="%(asctime)s [%(levelname)s] %(message)s",
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datefmt="%Y-%m-%d %H:%M:%S"
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)
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# Initialize printer
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try:
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printer = USBPrinter(args.device)
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printer.connect()
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except RuntimeError as e:
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logger.error(f"Failed to initialize printer: {e}")
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sys.exit(1)
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# Create and run bridge
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bridge = PrinterBridge(printer, args.host, args.port)
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# Handle shutdown signals
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loop = asyncio.get_event_loop()
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def shutdown():
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logger.info("Shutting down...")
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loop.create_task(bridge.stop())
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for sig in (signal.SIGINT, signal.SIGTERM):
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loop.add_signal_handler(sig, shutdown)
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try:
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await bridge.start()
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except asyncio.CancelledError:
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pass
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finally:
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printer.close()
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logger.info("Bridge stopped")
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if __name__ == "__main__":
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asyncio.run(main())
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