GNU Radio MCP Server

An MCP (Model Context Protocol) server that bridges an LLM to a live GNU Radio SDR flowgraph. Control your software-defined radio — tune frequencies, adjust gain, capture IQ samples, analyse spectra, and sweep for signals — all through natural language via any MCP-compatible client.

Architecture

┌─────────────┐      MCP (stdio / HTTP)      ┌──────────────────┐
│   LLM /     │◄──────────────────────────────►│  gnuradio_mcp    │
│   Claude    │        tool calls &            │  MCP Server      │
│   Desktop   │        responses               │                  │
└─────────────┘                                └──┬──────────┬───┘
                                                  │          │
                                    XML-RPC       │          │  ZMQ SUB
                                    (control)     │          │  (IQ data)
                                                  ▼          ▼
                                            ┌────────────────────┐
                                            │    GNU Radio       │
                                            │    Companion       │
                                            │    Flowgraph       │
                                            │  ┌──────────────┐  │
                                            │  │ XMLRPC Server │  │
                                            │  │ ZMQ PUB Sink  │  │
                                            │  └──────────────┘  │
                                            └────────┬───────────┘
                                                     │
                                                     ▼
                                            ┌────────────────────┐
                                            │  SDR Hardware      │
                                            │  (HackRF / RTL-SDR │
                                            │   / USRP / Sim)    │
                                            └────────────────────┘

Quick Start (Simulation — No Hardware)

pip install gnuradio-mcp-server

# Open simulation_mcp.grc in GNU Radio Companion and click Run
# (provides two test tones at +10 kHz and +50 kHz from center)

gnuradio-mcp

Quick Start (HackRF)

pip install gnuradio-mcp-server

# Open hackrf_mcp.grc in GNU Radio Companion and click Run & ensure HackRF is connected

GNURADIO_HARDWARE=hackrf gnuradio-mcp

Claude Desktop Integration

Add the following to your claude_desktop_config.json:

{
  "mcpServers": {
    "gnuradio_mcp": {
      "command": "gnuradio-mcp",
      "args": [],
      "env": {
        "GNURADIO_HARDWARE": "hackrf",
        "GNURADIO_GR_HOST": "127.0.0.1",
        "GNURADIO_GR_XMLRPC_PORT": "8080",
        "GNURADIO_GR_ZMQ_PORT": "5555"
      }
    }
  }
}

For HTTP transport:

{
  "mcpServers": {
    "gnuradio_mcp": {
      "url": "http://127.0.0.1:8000/mcp",
      "transport": "streamable-http"
    }
  }
}

Tools Reference

#	Tool Name	Description	Read-Only
1	gnuradio_flowgraph_start	Start the GNU Radio flowgraph	No
2	gnuradio_flowgraph_stop	Stop the GNU Radio flowgraph	No
3	gnuradio_flowgraph_status	Get flowgraph status and current parameters	Yes
4	gnuradio_set_center_frequency	Set the SDR center frequency	No
5	gnuradio_set_sample_rate	Set the SDR sample rate	No
6	gnuradio_set_gain	Set the SDR gain (IF/RF/BB stages)	No
7	gnuradio_set_variable	Set an arbitrary flowgraph variable	No
8	gnuradio_get_variable	Read an arbitrary flowgraph variable	Yes
9	gnuradio_list_variables	List all flowgraph variables	Yes
10	gnuradio_capture_samples	Capture IQ samples and return a power summary	Yes
11	gnuradio_get_spectrum_snapshot	FFT/PSD analysis with peak detection	Yes
12	gnuradio_detect_signals	Sweep a frequency range and detect active signals	Yes
13	gnuradio_ping	Health check (XML-RPC + ZMQ connectivity)	Yes

Environment Variables

All variables use the GNURADIO_ prefix:

Variable	Default	Description
GNURADIO_GR_HOST	127.0.0.1	GNU Radio host address
GNURADIO_GR_XMLRPC_PORT	8080	XML-RPC server port
GNURADIO_GR_ZMQ_PORT	5555	ZMQ PUB sink port
GNURADIO_GR_XMLRPC_TIMEOUT	5	XML-RPC timeout in seconds
GNURADIO_GR_ZMQ_TIMEOUT_MS	3000	ZMQ receive timeout in ms
GNURADIO_HARDWARE	hackrf	Hardware type: hackrf/rtlsdr/usrp/simulation
GNURADIO_FREQ_MIN_HZ	1000000	Minimum tunable frequency (Hz)
GNURADIO_FREQ_MAX_HZ	6000000000	Maximum tunable frequency (Hz)
GNURADIO_GAIN_MIN_DB	0	Minimum gain (dB)
GNURADIO_GAIN_MAX_DB	62	Maximum gain (dB)
GNURADIO_SAMP_RATE_MIN	100000	Minimum sample rate (sps)
GNURADIO_SAMP_RATE_MAX	20000000	Maximum sample rate (sps)
GNURADIO_DEFAULT_SAMP_RATE	2000000	Default sample rate for DSP
GNURADIO_TRANSPORT	stdio	Transport: stdio / streamable_http
GNURADIO_HTTP_PORT	8000	HTTP transport port

Edge Cases & Known Limitations

1. Sample rate restart: Some SDR hardware (especially RTL-SDR) requires a flowgraph restart after changing the sample rate. The gnuradio_set_sample_rate tool includes a warning about this.

2. ZMQ dtype requirement: The ZMQ PUB Sink in your flowgraph must output complex64 (8 bytes per sample). Misaligned data will raise a GRHardwareError.

3. Frequency clamping: Frequencies outside the configured [freq_min_hz, freq_max_hz] range are rejected before being sent to hardware. Adjust the env vars for your specific hardware.

4. Context overflow warning: Capturing more than 65,536 IQ samples triggers a warning, as the response summary may still be large. Use gnuradio_get_spectrum_snapshot for analysed results instead.

5. XML-RPC not thread-safe: A new ServerProxy is created per RPC call to avoid shared-state bugs in async contexts.

6. ZMQ socket lifecycle: Each recv_samples call opens and closes its own ZMQ SUB socket. This is intentional — the slight overhead avoids shared-socket state issues.

Development

# Install in development mode
pip install -e ".[dev]"

# Run tests
pytest tests/ -v

# Run with HTTP transport
GNURADIO_TRANSPORT=streamable_http python -m gnuradio_mcp.server

License

MIT