Introduce sensord simulator

testbench/.gitignore

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+*.egg-info
+*.py?
+.mypy_cache

testbench/Makefile

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+mypy:
+	mypy variodtb
+
+black:
+	black setup.py variodtb

testbench/Pipfile

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+[[source]]
+name = "pypi"
+url = "https://pypi.org/simple"
+verify_ssl = true
+
+[dev-packages]
+black = "*"
+mypy = "*"
+
+[packages]
+variod-testbench = {editable = true,path = "."}
+
+[pipenv]
+allow_prereleases = true

testbench/README.md

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+# Test bench for variod
+
+`variod` relies on `sensord` to supply with vario input. Instead of running a
+real `sensord` daemon on real hardware, a simulator can be used. `variod`
+generates vario sound based on input from `sensord` and forwards NMEA traffic
+to XCSoar. So, there are total 3 processes involved in a typical operating
+environment:
+
+* `sensord` - connects to variod on TCP port 4353
+* `variod` - listens TCP port 4353 and forwards traffic to port 4352
+* `xcsoar` - listens on TCP port 4352
+
+Traffic flow can be described in diagram:
+
+```
++---------+         +--------+        +--------+
+|         |         |        +-------->        |
+| sensord +---------> variod |        | xcsoar |
+|         |         |        <--------+        |
++---------+         +--------+        +--------+
+```
+
+This project provides tools for testing variod daemon by simulating other parts
+of the equation (`sensord` and `xcsoar`)
+
+## Setting up environment
+
+Development environment is managed by `pipenv`, so you need to install it
+first:
+
+```
+pip3 install pipenv
+```
+
+Then development environment can be initialized by running
+
+```
+pipenv install
+```
+
+## Running
+
+Before running any command, set up your shell with:
+
+```
+pipenv shell
+```
+
+After that, the following commands should become available:
+
+* `sensord-sim` - simulator for real sensor daemon
+
+### Quick start
+
+Run thesse commands in 3 separate terminals:
+
+| Terminal 1    | Terminal 2     | Terminal 3             |
+|---------------|----------------|------------------------|
+| `nc -lp 4352` | `../variod -f` | `sensord-sim generate` |
+
+### Simulating sensord
+
+`sensord-sim` replaces `sensord` process. Sensord suports several modes via command line options.
+
+`generate` mode generates NMEA stream that goes from minimum vario reading to
+maximum and back periodically. For example:
+
+```
+seonsord-sim generate --min=2 --max=5 --period=10
+```
+
+`replay` mode simply forwards NMEA stream from pre-recorded file
+
+```
+seonsord-sim replay samples/sample_flight_2.nmea
+```
+
+It also allows to configure the delay between each sentence sent using
+`--delay` flag.  For example, to stress-test variod, one can flood it with NMEA
+messages by setting the delay to 0:
+
+```
+sensord-sim --delay=0 replay samples/sample_flight_2.nmea
+```
+
+See `sensord-sim --help` for the full list of options.
+
+### Simulating xcsoar
+
+The most primitive way to simulate `xcsoar` process is to listen for port 4352
+using netcat command:
+
+```
+nc -lp 4352
+```
+
+One can also run the actual xcsoar command and configure the openvario device
+on port 4352.