nano-mcp-termux

nano-mcp-termux

Zero-dependency, single-file MCP server for AI agents, natively running on Termux (Android), Raspberry Pi, and Linux.

🚀 Quick Start

Local (Termux / Linux)

cd /path/to/nano-mcp-termux
python3 nano_mcp_termux.py

Docker

docker build -t nano-mcp-termux .
docker run -i --rm nano-mcp-termux

Health check (one-shot, no MCP handshake)

python3 nano_mcp_termux.py --health

🛠️ Features

• ✅ Zero-dependency: No external packages required
• ✅ Single-file: All logic in one Python script
• ✅ Cross-platform: Works in Termux (Android), on Raspberry Pi, Linux, and inside Docker
• ✅ Container-ready: Dockerfile at repo root for Glama introspection
• ✅ Standard stdio framing: Newline-delimited JSON-RPC (official MCP transport)
• ✅ Version negotiation: Echoes client protocolVersion (2024-11-05 / 2025-06-18 / 2025-11-25), falls back to highest supported
• ✅ Graceful degradation: device_status never fails; unavailable inputs are marked, not crashed
• ✅ [lifecycle] No orphaned processes: every command runs in its own process group; timeouts kill the whole tree (SIGTERM → SIGKILL), never just the shell
• ✅ [lifecycle] Self-terminating: parent-process watchdog + stdin-EOF detection + optional idle timeout, so a dead client never leaves a zombie server behind
• ✅ [lifecycle] Phantom Process Killer aware: reports Android 12+ child-count risk with concrete mitigations
• ✅ [paths] Android/Termux path adapter: resolves /sdcard ↔ /storage/emulated/0 ↔ $HOME/storage/shared, detects noexec mounts, case-insensitive filesystems, and shell-quoting hazards

🧩 Tools Overview

Tool	Description
device_status	Aggregate device info: battery / storage / arch / memory (degraded fields marked unavailable)
server_health	Runtime health: pid/ppid/env, uptime, request counters, live children, reaping policy, RSS, Phantom Process Killer risk
resolve_path	Resolve an Android/Termux path: canonical form, mount point, noexec/read-only flags, case sensitivity, equivalent spellings, quoting warnings
path_adapter	Environment profile: runtime class, $HOME/$PREFIX/$TMPDIR, Android storage roots with mount summaries, noexec mount list

🔗 Protocol Surface

Method	Behavior
initialize	Echoes supported client version (2024-11-05 / 2025-06-18 / 2025-11-25), else responds with highest supported per MCP spec; declares {"tools": {}}
notifications/initialized	Silent (no response)
ping	Returns {}
tools/list	Returns tool catalog
tools/call	Returns {"content": [{"type": "text", ...}]}
Unknown method / tool	-32601 / -32602 JSON-RPC errors
Malformed JSON	-32700 parse error

🔄 Why 1.1.0: the orphan-process bug

Version 1.0.0 ran commands with subprocess.run(..., timeout=...). On timeout, Python terminates only the direct child — the sh -c wrapper. Anything the shell had already spawned is reparented to init and survives forever. On Android that is the exact leak class that trips the Phantom Process Killer and can get the whole app group killed.

1.1.0 fixes this at the root: commands are spawned with start_new_session=True and torn down with os.killpg(pgid, SIGTERM) → SIGKILL, so the entire process tree dies together.

The repository ships a reproducible A/B regression test for it:

python3 test_lifecycle_orphan.py
# current  nano_mcp_termux.py           leaked_grandchildren=0
# legacy   nano_mcp_termux_v10_backup.py leaked_grandchildren=1   <- the bug
# PASS: current server leaves 0 orphaned grandchildren after timeout

✅ Tests

python3 test_client.py            # 32 protocol / tool / lifecycle assertions
python3 test_lifecycle_orphan.py  # orphan-leak A/B regression (1.0.0 vs 1.1.0)

⚙️ Environment variables

Variable	Default	Purpose
NANO_IDLE_TIMEOUT	0 (off)	Seconds of inactivity before the server exits on its own
NANO_NO_WATCHDOG	unset	Set to 1 to disable the parent-process watchdog thread

🔗 Links

• Original repository: Lmeng486/nano-mcp-termux
• Verification report: awesome-termux-mcp

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This server is designed to pass Glama introspection checks and serve as a lightweight MCP implementation for mobile and edge devices.