SWTbahn Client-Server Command Line Interface

This is a client-server command line interface for the SWTbahn. The server is connected to the BiDiB interface and provides a REST API. The client side provides a command line interface which connects to the web service to execute the commands. The command line interface was developed by Nicolas Gross as part of his work for the libbidib project.

Dependencies

Server

• C compiler
• Libraries: onion, libpam, libgnutls, libgcrypt, libpthread, libglib-2.0, libyaml, libbidib
• ForeC command line compiler: forecc
• KIELER command line compiler: kico.jar
  • Path to the folder that contains kico.jar has to be defined in the environment variable KIELER_PATH
• BahnDSL command line compiler: bahnc
  • Path to the folder that contains the bahnc has to be defined in the environment variable BAHNDSL_PATH
• SCCharts verifier: SWTbahn Verifier (SWT internal repository)

Command Line Client

• python3
• Python libraries: click, requests, pyaml (pip3 install click requests pyaml)

Web Client

• Web browser

Build

1. Clone the repository
2. Install the necessary dependencies (remember to run ldconfig after make install for libbidib if you are on Linux)
3. Navigate to the directory where the build files should be generated
4. Execute cmake <path-to-project-root>/server
5. Execute make

Test

To run the unit tests, execute make test from within the build directory. Each unit test can be executed to display more detailed test results, e.g., ./server_bahn_util_tests.

Usage

Server

0. Build the executable (see section Build)
1. Create the configuration files for your track (see libbidib documentation)
2. Connect the BiDiB interface to the server
3. Check on which serial device the board is connected: dmesg | grep tty
4. Start the server: ./swtbahn-server <serial-device> <config-directory> <IP> <port> (IP is the IP-address under which the server can be reached and port specifies on which port the server listens)
   For example: ./swtbahn-server /dev/ttyUSB0 ../../configurations/swtbahn-lite/ 141.13.106.27 2048
5. Quit the server with Ctrl-C if you're done

Client (Command Line)

0. The client is located under <project-root>/client/swtbahn

1. Use the --help flag to get information about parameters, options, ...

2. Use the config command to setup the client: swtbahn config <hostname> <port> <default-track-output>, where hostname is the IP and port the port which you used when you started the server. The is the name of the track output which should be used if no track output is explicitly specified when issuing a command.
   For example: ./swtbahn config 141.13.106.27 2048 master
   This will create a config file in the current working directory. Dont use the client from a different working directory for the current session, otherwise it won't find the configuration file. If you really want to use two logically different clients on the same device, you could just run the clients from different working directories which will lead to distinct configs.

3. Now you can use the commands from the categories swtbahn admin, swtbahn controller, swtbahn driver and swtbahn monitor. If the system was not started by swtbahn admin startup, all the other commands won't work.

   For example:
   ./swtbahn admin startup
./swtbahn monitor get_segments
./swtbahn monitor get_trains
./swtbahn driver grab cargo
./swtbahn driver set_dcc_speed -b 5

4. If you're done, you should shut the system down gracefully by invoking swtbahn admin shutdown

Client (Web Interface)

0. Use a web browser to navigate to <IP>:<port>/assets/client.html
1. Set the main track output (default is master).
2. Click the Startup button.
3. To be a train driver, select a train and click the Grab button. Enter a speed between 0 (stop) and 127 (max speed), and click the Drive button.
4. To control a point, type the name of a point (see the YAML configuration file), select a position, and click the Set button.
5. To control a signal, type the name of a signal (see the YAML configuration file), select an aspect, and click the Set button.

Logging into the Raspberry Pi remotely

Use ssh to the log in remotely. Suppose the Raspberry Pi is located at 141.13.106.30. Then use the command ssh pi@141.13.106.30.

Strategy for finding the IP address of the Raspberry Pi

There are two Raspberry Pis with the hostnames raspberrypi1 and raspberrypi2. The Raspberry Pi documentation lists several strategies for finding the IP address of a Raspberry Pi. If you change the Raspberry Pi's hostname, e.g., by editing /etc/hostname or by using the Raspberry Pi Configuration application, Avahi will automatically change the .local mDNS address. The MAC address of all Raspberry Pis begin with b8:27:eb.

1. macOS: Try and resolve the Raspberry Pi's hostname, e.g., raspberrypi1.local, with multicast DNS:

   ping raspberrypi1.local

   If this fails, try the strategy for Linux.

2. Linux: Use ifconfig to find your subnet, e.g., 192.168.1._. Use the nmap command to scan your subnet for connected devices, and look for the Raspberry Pi's hostname in the results:

   nmap -sn 192.168.1.0/24

3. Windows: Use ipconfig to find your subnet, e.g., 192.168.1._. Install nmap and open the command line as an administrator for nmap to display the hostnames in its results. Use the nmap command to scan your subnet for connected devices, and look for the Raspberry Pi's hostname in the results:

   nmap -sn 192.168.1.0/24

   Use the command nmap -sn 192.168.1.0/24 | findstr /i "b8:27:eb" to quickly see a list of Raspberry Pis (MAC addresses only).

Sending files from the Raspberry Pi to a client computer:

Use scp on your client computer. For example, suppose the Raspberry Pi is located at 141.13.106.30 and has the user pi. To copy the the file /var/log/syslog from the Raspberry Pi via the user pi, use the command scp pi@141.13.106.30:/var/log/syslog syslog

Verification

Train engines (and ther plugins) defined as SCCharts (*.sctx) files can be verified against certain properties before they are uploaded to the sever. Verification is on by default and can be configured to true (On) or false (Off) via the /admin/set-verification-option endpoint. For the command line client, use the command swtbahn admin set-verification-option <true/false>.

When verification has been turned on and an SCCharts file is uploaded, the server sends a request to SWTbahn Verifier (SWT internal repository), which...

1. checks that the SCCharts file defines a set of safety properties (invariants, LTLs),
2. compiles the SCCharts file to a format that can be verified (e.g., using nuSmv),
3. verifies the safety properties, and
4. sends verification results back to the server.

If all safety properties hold, the server processes the SCCharts file, e.g., by compiling and loading the file as a plugin. Otherwise, if any safety property does not hold, the server does not process the SCCharts file any further and reports the failure to the client.

The sever communicates with SWTbahn Verifier via websockets with JSON messages. A typical verification session is as follows:

1. swtbahn-cli server receives an upload request for an SCCharts file;
2. swtbahn-cli server establishes a websocket connection with SWTbahn Verifier;
3. swtbahn-cli server sends the SCCharts file as a JSON message to SWTbahn Verifier;
4. SWTbahn Verifier responds by either
   1. acknowledging the request to verify the SCCharts file and proceeding with the verification, or
   2. rejecting the request;
5. swtbahn-cli responds by either
   1. waiting for the verification results on the websocket connection, or
   2. stopping the processing of the SCCharts file;
6. for the case that SWTbahn Verifier proceeded with the verification, after the verification has finished, SWTbahn Verifier sends the results as a JSON message to the swtbahn-cli server; and
7. swtbahn-cli receives the results, closes the websocket connection, and processes the results.

Grab-id and session-id behaviour

Grab-ids are used as tokens for trains. A client needs to grab a train before he can invoke commands for controlling the train. A train could only be grabbed by one client at a time.
Session-ids are used to check wether a grab-id was given out to the client on the current session or on a previous session.

Server side

When is a new session-id created?

• If a user issues swtbahn admin startup and the system is not running already

When is the session-id invalidated?

• If a user issues swtbahn admin shutdown

When is a grab-id created?

• If a client issues swtbahn driver grab <train> and the train is available

When is a grab-id invalidated?

• If a client issues swtbahn driver release and the train was grabbed by this client

Client side

When is the session-id fetched?

• If the user issues swtbahn driver grab <train> and the train is available and the client has not already grabbed a train

When is the session-id reset?

• If the user issues swtbahn driver release
• If the user issues any swtbahn driver command and the session-id or grab-id is not the same as the one at the server
• If the user issues swtbahn admin shutdown and the system was running
• If the user issues swtbahn config

When is a grab-id fetched?

• If the user issues swtbahn driver grab <train> and the train is available and the client has not already grabbed a train

When is a grab-id reset?

• If the user issues swtbahn driver release
• If the user issues any swtbahn driver command and the session-id or grab-id is not the same as the one at the server
• If the user issues swtbahn admin shutdown and the system was running
• If the user issues swtbahn config

Logging Format Notes

We try to use a consistent logging format in all request handlers. General workflow of how request handlers generate log messages:

1. Parse form data.
2. Validate form data. If validation fails, make a log on ERROR level and stop processing.
3. Make a log on log level NOTICE that represents the start of processing, with - start at the end of the log.
4. Process request. If processing causes an error, make a log on the ERROR or WARNING log level with - abort at the end of the log and stop processing.
5. Processing concluded. Indicate this by printing the log message of Step 3 again, on the same log level, with - finish instead of - start at the end.

For request handlers that barely do any "processing" at all; e.g. where only a status variable is updated, they only generate one log message that ends with - done. Request handlers that only return information (getters) also use the - done pattern instead of start and finish, and use the log level INFO for the - done log.

As an example, when a request is made to set point10 to the normal state, the request handler (handler_set_point) generates the following log messages when the processing is successful:

LOG_NOTICE: Request: Set point - point: point10 state: normal - start
Intervening log messages from internal processing
LOG_NOTICE: Request: Set point - point: point10 state: normal - finish

If the above request was instead made with an unsupported state, e.g., foobar, then the request handler would generate the following log messages to say that the processing was stopped because of invalid parameters:

LOG_NOTICE: Request: Set point - point: point10 state: foobar - start
Intervening log messages from internal processing
LOG_ERR: Request: Set point - point: point10 state: foobar - invalid parameters - abort

If the above request forgot to specify the state, i.e., the state parameter is null, then the request handler would only generate the following log message to say that the parameter validation failed:

LOG_ERR: Request: Set point - invalid parameters