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catarrh 73b0277ef7 Initial commit: simtrace2-pysniff v0.1.0

Python-based SIMtrace2 sniffer — drop-in replacement for simtrace2-sniff.
Single dependency (pyusb), auto-reconnect, GSMTAP/PCAP output, library API.

Modules:
  protocol.py — SIMtrace2 USB sniffing protocol parser
  device.py   — USB discovery + SniffSession with exponential backoff reconnect
  gsmtap.py   — GSMTAP UDP sender for Wireshark
  pcap.py     — PCAP file writer (LINKTYPE_GSMTAP)
  dump.py     — hex dump formatters + file output
  __main__.py — CLI entry point

Startup script sniff-start.sh handles udev permission checks and shows
install instructions. udev rule uses TAG+=uaccess (systemd-logind ACL).

2026-08-10 23:17:04 +03:00

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simtrace2-pysniff

Python-based replacement for simtrace2-sniff — SIM card communication sniffer for Osmocom SIMtrace2 hardware (firmware in trace mode).

Single dependency: PyUSB (libusb wrapper). No libosmocore, no libosmosim.

Quick Start

# Install + run
pip install pyusb
python -m simtrace2_pysniff

Or use the bundled startup script:

./sniff-start.sh                                 # hex dump to stdout
./sniff-start.sh --gsmtap 127.0.0.1:4729         # + Wireshark GSMTAP
./sniff-start.sh --pcap trace.pcap               # save PCAP for later
./sniff-start.sh --inactivity-timeout 30         # reconnect on silence

The startup script performs a pre-flight USB permission check and prints install instructions if the udev rule is missing (see below).

USB Device Access

Linux

A udev rule is required for non-root USB access to the SIMtrace2 device.

sudo cp 70-simtrace2-pysniff.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules
sudo udevadm trigger

Then reconnect the SIMtrace2 USB cable. The rule uses TAG+="uaccess" (systemd-logind ACL) — no group membership or world-writable permissions needed.

Windows

Windows does not ship a libusb-compatible driver for SIMtrace2. Use Zadig to replace the default driver:

Download and run Zadig
Plug in the SIMtrace2 device
Select it in the dropdown (VID 1D50, PID 60E3 — "Osmocom SIMtrace 2")
Choose WinUSB (or libusbK) as the replacement driver
Click Replace Driver (one-time operation)

After that, python -m simtrace2_pysniff works identically to Linux.

CLI Options

python -m simtrace2_pysniff [OPTIONS]

  --gsmtap HOST[:PORT]      Send ATR/TPDU as GSMTAP over UDP (default port 4729)
  --pcap FILE               Write sniffed data to PCAP file for Wireshark
  --output, -o FILE         Write hex dump to file
  --no-stdout               Suppress hex dump to stdout
  --vendor HEX              USB vendor ID (default: 0x1d50)
  --product HEX             USB product ID (default: auto-detect)

Recovery options:
  --no-reconnect            Exit on USB disconnect instead of reconnecting
  --inactivity-timeout SEC  Reconnect after N seconds of silence (default: disabled)

Library Usage

from simtrace2_pysniff import SniffSession

session = SniffSession(inactivity_timeout=30.0)
for msg in session.iter_messages():
    print(f"{msg.type}: {msg.data.hex()}")

Output

stdout: ATR: 3b 9e ..., TPDU: a0 a4 00 00 02 3f 00, Card state change: reset de-asserted
GSMTAP: ATR (subtype 1) and TPDU (subtype 2) over UDP to Wireshark
PCAP: all messages as GSMTAP-encapsulated packets (LINKTYPE 155), openable in Wireshark

Recovery

The tool survives hardware resets, cable disconnects, and firmware hangs by default — it reconnects with exponential backoff (1s → 30s cap). Use --inactivity-timeout to also trigger reconnect on silent firmware hangs.

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