feat: add rtl_tcp remote SDR support to aprs, morse, and dsc routes

Closes #164. Only pager and sensor routes supported rtl_tcp connections.
Now aprs, morse, and dsc routes follow the same pattern: extract
rtl_tcp_host/port from the request, skip local device claiming for
remote connections, and use SDRFactory.create_network_device(). DSC also
refactored from manual rtl_fm command building to use SDRFactory's
builder abstraction. Frontend wired up for all three modes.

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

routes/aprs.py

@@ -22,7 +22,13 @@ from flask import Blueprint, jsonify, request, Response
 
 import app as app_module
 from utils.logging import sensor_logger as logger
-from utils.validation import validate_device_index, validate_gain, validate_ppm
+from utils.validation import (
+    validate_device_index,
+    validate_gain,
+    validate_ppm,
+    validate_rtl_tcp_host,
+    validate_rtl_tcp_port,
+)
 from utils.sse import sse_stream_fanout
 from utils.event_pipeline import process_event
 from utils.sdr import SDRFactory, SDRType
@@ -1689,6 +1695,10 @@ def start_aprs() -> Response:
     except ValueError as e:
         return jsonify({'status': 'error', 'message': str(e)}), 400
 
+    # Check for rtl_tcp (remote SDR) connection
+    rtl_tcp_host = data.get('rtl_tcp_host')
+    rtl_tcp_port = data.get('rtl_tcp_port', 1234)
+
     sdr_type_str = str(data.get('sdr_type', 'rtlsdr')).lower()
     try:
         sdr_type = SDRType(sdr_type_str)
@@ -1708,16 +1718,17 @@ def start_aprs() -> Response:
                 'message': f'rx_fm not found. Install SoapySDR tools for {sdr_type.value}.'
             }), 400
 
-    # Reserve SDR device to prevent conflicts with other modes
-    error = app_module.claim_sdr_device(device, 'aprs', sdr_type_str)
-    if error:
-        return jsonify({
-            'status': 'error',
-            'error_type': 'DEVICE_BUSY',
-            'message': error
-        }), 409
-    aprs_active_device = device
-    aprs_active_sdr_type = sdr_type_str
+    # Reserve SDR device to prevent conflicts (skip for remote rtl_tcp)
+    if not rtl_tcp_host:
+        error = app_module.claim_sdr_device(device, 'aprs', sdr_type_str)
+        if error:
+            return jsonify({
+                'status': 'error',
+                'error_type': 'DEVICE_BUSY',
+                'message': error
+            }), 409
+        aprs_active_device = device
+        aprs_active_sdr_type = sdr_type_str
 
     # Get frequency for region
     region = data.get('region', 'north_america')
@@ -1741,8 +1752,17 @@ def start_aprs() -> Response:
 
     # Build FM demod command for APRS (AFSK1200 @ 22050 Hz) via SDR abstraction.
     try:
-        sdr_device = SDRFactory.create_default_device(sdr_type, index=device)
-        builder = SDRFactory.get_builder(sdr_type)
+        if rtl_tcp_host:
+            try:
+                rtl_tcp_host = validate_rtl_tcp_host(rtl_tcp_host)
+                rtl_tcp_port = validate_rtl_tcp_port(rtl_tcp_port)
+            except ValueError as e:
+                return jsonify({'status': 'error', 'message': str(e)}), 400
+            sdr_device = SDRFactory.create_network_device(rtl_tcp_host, rtl_tcp_port)
+            logger.info(f"Using remote SDR: rtl_tcp://{rtl_tcp_host}:{rtl_tcp_port}")
+        else:
+            sdr_device = SDRFactory.create_default_device(sdr_type, index=device)
+        builder = SDRFactory.get_builder(sdr_device.sdr_type)
         rtl_cmd = builder.build_fm_demod_command(
             device=sdr_device,
             frequency_mhz=float(frequency),

routes/dsc.py

@@ -37,7 +37,12 @@ from utils.database import (
 from utils.dsc.parser import parse_dsc_message
 from utils.sse import sse_stream_fanout
 from utils.event_pipeline import process_event
-from utils.validation import validate_device_index, validate_gain
+from utils.validation import (
+    validate_device_index,
+    validate_gain,
+    validate_rtl_tcp_host,
+    validate_rtl_tcp_port,
+)
 from utils.sdr import SDRFactory, SDRType
 from utils.dependencies import get_tool_path
 from utils.process import register_process, unregister_process
@@ -336,19 +341,29 @@ def start_decoding() -> Response:
         # Get SDR type from request
         sdr_type_str = data.get('sdr_type', 'rtlsdr')
 
-        # Check if device is available using centralized registry
-        global dsc_active_device, dsc_active_sdr_type
-        device_int = int(device)
-        error = app_module.claim_sdr_device(device_int, 'dsc', sdr_type_str)
-        if error:
-            return jsonify({
-                'status': 'error',
-                'error_type': 'DEVICE_BUSY',
-                'message': error
-            }), 409
+        # Check for rtl_tcp (remote SDR) connection
+        rtl_tcp_host = data.get('rtl_tcp_host')
+        rtl_tcp_port = data.get('rtl_tcp_port', 1234)
 
-        dsc_active_device = device_int
-        dsc_active_sdr_type = sdr_type_str
+        try:
+            sdr_type = SDRType(sdr_type_str)
+        except ValueError:
+            sdr_type = SDRType.RTL_SDR
+
+        # Check if device is available using centralized registry (skip for remote rtl_tcp)
+        global dsc_active_device, dsc_active_sdr_type
+        if not rtl_tcp_host:
+            device_int = int(device)
+            error = app_module.claim_sdr_device(device_int, 'dsc', sdr_type_str)
+            if error:
+                return jsonify({
+                    'status': 'error',
+                    'error_type': 'DEVICE_BUSY',
+                    'message': error
+                }), 409
+
+            dsc_active_device = device_int
+            dsc_active_sdr_type = sdr_type_str
 
         # Clear queue
         while not app_module.dsc_queue.empty():
@@ -357,22 +372,32 @@ def start_decoding() -> Response:
             except queue.Empty:
                 break
 
-        # Build rtl_fm command
-        rtl_fm_path = tools['rtl_fm']['path']
+        # Build rtl_fm command via SDR abstraction layer
         decoder_path = tools['dsc_decoder']['path']
 
-        # rtl_fm command for DSC decoding
-        # DSC uses narrow FM at 156.525 MHz with 48kHz sample rate
-        rtl_cmd = [
-            rtl_fm_path,
-            '-f', f'{DSC_VHF_FREQUENCY_MHZ}M',
-            '-s', str(DSC_SAMPLE_RATE),
-            '-d', str(device),
-            '-g', str(gain),
-            '-M', 'fm',           # FM demodulation
-            '-l', '0',            # No squelch for DSC
-            '-E', 'dc'            # DC blocking filter
-        ]
+        if rtl_tcp_host:
+            try:
+                rtl_tcp_host = validate_rtl_tcp_host(rtl_tcp_host)
+                rtl_tcp_port = validate_rtl_tcp_port(rtl_tcp_port)
+            except ValueError as e:
+                return jsonify({'status': 'error', 'message': str(e)}), 400
+            sdr_device = SDRFactory.create_network_device(rtl_tcp_host, rtl_tcp_port)
+            logger.info(f"Using remote SDR: rtl_tcp://{rtl_tcp_host}:{rtl_tcp_port}")
+        else:
+            sdr_device = SDRFactory.create_default_device(sdr_type, index=int(device))
+
+        builder = SDRFactory.get_builder(sdr_device.sdr_type)
+        rtl_cmd = list(builder.build_fm_demod_command(
+            device=sdr_device,
+            frequency_mhz=DSC_VHF_FREQUENCY_MHZ,
+            sample_rate=DSC_SAMPLE_RATE,
+            gain=float(gain) if gain and str(gain) != '0' else None,
+            modulation='fm',
+            squelch=0,
+        ))
+        # Ensure trailing '-' for stdin piping and add DC blocking filter
+        if rtl_cmd and rtl_cmd[-1] == '-':
+            rtl_cmd = rtl_cmd[:-1] + ['-E', 'dc', '-']
 
         # Decoder command
         decoder_cmd = [decoder_path]

routes/morse.py

@@ -28,6 +28,8 @@ from utils.validation import (
     validate_frequency,
     validate_gain,
     validate_ppm,
+    validate_rtl_tcp_host,
+    validate_rtl_tcp_port,
 )
 
 morse_bp = Blueprint('morse', __name__)
@@ -279,6 +281,10 @@ def start_morse() -> Response:
 
     sdr_type_str = data.get('sdr_type', 'rtlsdr')
 
+    # Check for rtl_tcp (remote SDR) connection
+    rtl_tcp_host = data.get('rtl_tcp_host')
+    rtl_tcp_port = data.get('rtl_tcp_port', 1234)
+
     with app_module.morse_lock:
         if morse_state in {MORSE_STARTING, MORSE_RUNNING, MORSE_STOPPING}:
             return jsonify({
@@ -287,17 +293,19 @@ def start_morse() -> Response:
                 'state': morse_state,
             }), 409
 
-        device_int = int(device)
-        error = app_module.claim_sdr_device(device_int, 'morse', sdr_type_str)
-        if error:
-            return jsonify({
-                'status': 'error',
-                'error_type': 'DEVICE_BUSY',
-                'message': error,
-            }), 409
+        # Reserve SDR device (skip for remote rtl_tcp)
+        if not rtl_tcp_host:
+            device_int = int(device)
+            error = app_module.claim_sdr_device(device_int, 'morse', sdr_type_str)
+            if error:
+                return jsonify({
+                    'status': 'error',
+                    'error_type': 'DEVICE_BUSY',
+                    'message': error,
+                }), 409
 
-        morse_active_device = device_int
-        morse_active_sdr_type = sdr_type_str
+            morse_active_device = device_int
+            morse_active_sdr_type = sdr_type_str
         morse_last_error = ''
         morse_session_id += 1
 
@@ -320,23 +328,35 @@ def start_morse() -> Response:
     except ValueError:
         sdr_type = SDRType.RTL_SDR
 
+    # Create network or local SDR device
+    network_sdr_device = None
+    if rtl_tcp_host:
+        try:
+            rtl_tcp_host = validate_rtl_tcp_host(rtl_tcp_host)
+            rtl_tcp_port = validate_rtl_tcp_port(rtl_tcp_port)
+        except ValueError as e:
+            return jsonify({'status': 'error', 'message': str(e)}), 400
+        network_sdr_device = SDRFactory.create_network_device(rtl_tcp_host, rtl_tcp_port)
+        logger.info(f"Using remote SDR: rtl_tcp://{rtl_tcp_host}:{rtl_tcp_port}")
+
     requested_device_index = int(device)
     active_device_index = requested_device_index
-    builder = SDRFactory.get_builder(sdr_type)
+    builder = SDRFactory.get_builder(network_sdr_device.sdr_type if network_sdr_device else sdr_type)
 
     device_catalog: dict[int, dict[str, str]] = {}
     candidate_device_indices: list[int] = [requested_device_index]
-    with contextlib.suppress(Exception):
-        detected_devices = SDRFactory.detect_devices()
-        same_type_devices = [d for d in detected_devices if d.sdr_type == sdr_type]
-        for d in same_type_devices:
-            device_catalog[d.index] = {
-                'name': str(d.name or f'SDR {d.index}'),
-                'serial': str(d.serial or 'Unknown'),
-            }
-        for d in sorted(same_type_devices, key=lambda dev: dev.index):
-            if d.index not in candidate_device_indices:
-                candidate_device_indices.append(d.index)
+    if not network_sdr_device:
+        with contextlib.suppress(Exception):
+            detected_devices = SDRFactory.detect_devices()
+            same_type_devices = [d for d in detected_devices if d.sdr_type == sdr_type]
+            for d in same_type_devices:
+                device_catalog[d.index] = {
+                    'name': str(d.name or f'SDR {d.index}'),
+                    'serial': str(d.serial or 'Unknown'),
+                }
+            for d in sorted(same_type_devices, key=lambda dev: dev.index):
+                if d.index not in candidate_device_indices:
+                    candidate_device_indices.append(d.index)
 
     def _device_label(device_index: int) -> str:
         meta = device_catalog.get(device_index, {})
@@ -350,7 +370,7 @@ def start_morse() -> Response:
             tuned_frequency_mhz = max(0.5, float(freq))
         else:
             tuned_frequency_mhz = max(0.5, float(freq) - (float(tone_freq) / 1_000_000.0))
-        sdr_device = SDRFactory.create_default_device(sdr_type, index=device_index)
+        sdr_device = network_sdr_device or SDRFactory.create_default_device(sdr_type, index=device_index)
         fm_kwargs: dict[str, Any] = {
             'device': sdr_device,
             'frequency_mhz': tuned_frequency_mhz,