add frame logging and extract entry point to main.py

- msg/frame_logger.py: MsgListener that writes raw byte stream per
  source to timestamped log files (<YYYY_MM_DD_HH_MM_SS_source>.log)
- main.py: entry point extracted from network_backend.py; adds
  --log-dir argument (default ./log) and wires FrameLogger per transceiver
- network_backend.py: now contains only the NetworkBackend class
- .gitignore: exclude log/ directory

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -0,0 +1,135 @@
+import time
+import signal
+import argparse
+
+from network_backend import NetworkBackend
+from msg.frame_logger import FrameLogger
+from transceiver import Transceiver
+
+from nmea.packetizer import NmeaPacketizer
+from nmea.messages import Gll, Gsa, Gsv, Gga, Rmc
+
+from ubx.ubx import frame_create
+from ubx.msg_types import *
+from ubx.packetizer import UbxPacketizer
+from ubx.messages import Sig, Sat, RawX, UbxMsg
+from ubx.listener import UbxListener
+
+
+def handler(signum, frame, be: NetworkBackend, loggers: list):
+	sig_name = signal.Signals(signum).name
+	print(f'Signal handler called with signal {sig_name} ({signum})')
+	be.stop()
+	be.disconnect()
+	for lg in loggers:
+		lg.close()
+
+
+if __name__ == "__main__":
+	ap = argparse.ArgumentParser()
+	ap.add_argument('--log-dir', default='./log', help='Directory for frame log files (default: ./log)')
+	args = ap.parse_args()
+
+	server_list = [
+		{'name': " neo-f9p", 'host': "192.168.22.93", 'port': 8721},
+		{'name': "zed-x20p", 'host': "192.168.22.93", 'port': 8731}
+	]
+
+	transceiver = {}
+	loggers = []
+
+	# TCPIP multi source receiver
+	mc = NetworkBackend(server_list)
+
+	# Set the signal handler
+	signal.signal(signal.SIGINT, lambda signum, frame: handler(signum, frame, mc, loggers))
+
+	for grm in [" neo-f9p", "zed-x20p"]:
+		nmea_rx_list = [
+			Gll(grm, 'GN'),
+			Gsa(grm, 'GN'),
+			Gsv(grm, 'GP'),
+			Gga(grm, 'GP'),
+			Rmc(grm, 'GN'),
+			Gga(grm, 'GN'),
+		]
+		ubx_rx_list = [
+			UbxListener(Sig()),
+			UbxListener(Sat()),
+			UbxListener(RawX()),
+
+			UbxListener(UbxMsg(UBX_CLASS_ACK, UBX_ID_ACK_ACK)),
+			UbxListener(UbxMsg(UBX_CLASS_ACK, UBX_ID_ACK_NACK)),
+		]
+
+		# Topology
+		# Receiver-0.0 \
+		# Receiver-0.1 <- Packetizer-0 <- Transceiver-0 \
+		#                               /                \
+		#                      Send-0->/                  \
+		#                                                  + Backend
+		#                      Send-1->\                  /
+		#                               \                /
+		# Receiver-1.0 <- Packetizer-1 <- Transceiver-1 /
+		# Receiver-1.1 /
+
+		# Create transceiver
+		transceiver[grm] = Transceiver(grm)
+		mc.register_xcvr(transceiver[grm])
+
+		# Create and register frame logger
+		lg = FrameLogger(grm, args.log_dir)
+		loggers.append(lg)
+		transceiver[grm].register_listener(lg)
+
+		# Create NMEA-Packetizer
+		nmea_packetizer = NmeaPacketizer()
+		ubx_packetizer = UbxPacketizer()
+
+		# Register NMEA-Packetizer to transceiver
+		transceiver[grm].register_listener(nmea_packetizer)
+		transceiver[grm].register_listener(ubx_packetizer)
+
+		# Register Receiver to NMEA-Packetizer
+		for rx in nmea_rx_list:
+			nmea_packetizer.register_listener(rx)
+
+		# Register Receiver to UBX-Packetizer
+		for rx in ubx_rx_list:
+			ubx_packetizer.register_listener(rx)
+
+
+	# Connect all sources
+	mc.connect()
+
+	# Start thread
+	mc.start()
+
+	while True:
+		try:
+			for grm in [" neo-f9p", "zed-x20p"]:
+				# Poll UBX-NAV-CLOCK (0x01 0x22)
+				frame = frame_create(UBX_CLASS_NAV, UBX_ID_CLOCK)
+				transceiver[grm].send(frame)
+				# Poll UBX-NAV-SIG (0x01 0x43)
+				frame = frame_create(UBX_CLASS_NAV, UBX_ID_NAV_SIG)
+				transceiver[grm].send(frame)
+				# Poll UBX-NAV-SAT (0x01 0x35)
+				frame = frame_create(UBX_CLASS_NAV, UBX_ID_NAV_SAT)
+				transceiver[grm].send(frame)
+				# Poll UBX-RXM-RAWX (0x02 0x15)
+				frame = frame_create(UBX_CLASS_RXM, UBX_ID_RXM_RAW)
+				transceiver[grm].send(frame)
+		except ValueError:
+			break
+
+		time.sleep(1)
+
+	# Stop thread
+	mc.stop()
+
+	# code never reached
+	mc.disconnect()
+
+	for lg in loggers:
+		lg.close()