Merge remote-tracking branch 'origin/main' into request-reply-messaging-mode-tree

.gitignore

@@ -1,4 +1,5 @@
-/target
+target/
+
 /Cargo.lock
 
 /.idea/*

Cargo.toml

@@ -4,6 +4,7 @@ members = [
     "satrs",
     "satrs-mib",
     "satrs-example",
+    "satrs-minisim",
     "satrs-shared",
 ]
 

coverage.py

@@ -18,15 +18,19 @@ def generate_cov_report(open_report: bool, format: str, package: str):
     out_path = "./target/debug/coverage"
     if format == "lcov":
         out_path = "./target/debug/lcov.info"
-    os.system(
+    grcov_cmd = (
         f"grcov . -s . --binary-path ./target/debug/ -t {format} --branch --ignore-not-existing "
         f"-o {out_path}"
     )
+    print(f"Running: {grcov_cmd}")
+    os.system(grcov_cmd)
     if format == "lcov":
-        os.system(
+        lcov_cmd = (
             "genhtml -o ./target/debug/coverage/ --show-details --highlight --ignore-errors source "
             "--legend ./target/debug/lcov.info"
         )
+        print(f"Running: {lcov_cmd}")
+        os.system(lcov_cmd)
     if open_report:
         coverage_report_path = os.path.abspath("./target/debug/coverage/index.html")
         webbrowser.open_new_tab(coverage_report_path)
@@ -43,7 +47,7 @@ def main():
     parser.add_argument(
         "-p",
         "--package",
-        choices=["satrs"],
+        choices=["satrs", "satrs-minisim"],
         default="satrs",
         help="Choose project to generate coverage for",
     )

satrs-minisim/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "satrs-minisim"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+log = "0.4"
+thiserror = "1"
+
+[dependencies.asynchronix]
+version = "0.2.1"
+
+[dependencies.satrs]
+path = "../satrs"
+
+[dev-dependencies]
+delegate = "0.12"

satrs-minisim/src/acs.rs

@@ -0,0 +1,338 @@
+use std::{f32::consts::PI, sync::mpsc, time::Duration};
+
+use asynchronix::{
+    model::{Model, Output},
+    time::Scheduler,
+};
+use satrs::power::SwitchStateBinary;
+use satrs_minisim::{
+    acs::{MgmReply, MgmSensorValues, MgtDipole, MgtHkSet, MgtReply, MGT_GEN_MAGNETIC_FIELD},
+    SimReply,
+};
+
+use crate::time::current_millis;
+
+// Earth magnetic field varies between -30 uT and 30 uT
+const AMPLITUDE_MGM: f32 = 0.03;
+// Lets start with a simple frequency here.
+const FREQUENCY_MGM: f32 = 1.0;
+const PHASE_X: f32 = 0.0;
+// Different phases to have different values on the other axes.
+const PHASE_Y: f32 = 0.1;
+const PHASE_Z: f32 = 0.2;
+
+/// Simple model for a magnetometer where the measure magnetic fields are modeled with sine waves.
+///
+/// Please note that that a more realistic MGM model wouold include the following components
+/// which are not included here to simplify the model:
+///
+/// 1. It would probably generate signed [i16] values which need to be converted to SI units
+///    because it is a digital sensor
+/// 2. It would sample the magnetic field at a high fixed rate. This might not be possible for
+///    a general purpose OS, but self self-sampling at a relatively high rate (20-40 ms) might
+///    stil lbe possible.
+pub struct MagnetometerModel {
+    pub switch_state: SwitchStateBinary,
+    pub periodicity: Duration,
+    pub external_mag_field: Option<MgmSensorValues>,
+    pub reply_sender: mpsc::Sender<SimReply>,
+}
+
+impl MagnetometerModel {
+    pub fn new(periodicity: Duration, reply_sender: mpsc::Sender<SimReply>) -> Self {
+        Self {
+            switch_state: SwitchStateBinary::Off,
+            periodicity,
+            external_mag_field: None,
+            reply_sender,
+        }
+    }
+
+    pub async fn switch_device(&mut self, switch_state: SwitchStateBinary) {
+        self.switch_state = switch_state;
+    }
+
+    pub async fn send_sensor_values(&mut self, _: (), scheduler: &Scheduler<Self>) {
+        self.reply_sender
+            .send(SimReply::new(MgmReply {
+                switch_state: self.switch_state,
+                sensor_values: self.calculate_current_mgm_tuple(current_millis(scheduler.time())),
+            }))
+            .expect("sending MGM sensor values failed");
+    }
+
+    // Devices like magnetorquers generate a strong magnetic field which overrides the default
+    // model for the measured magnetic field.
+    pub async fn apply_external_magnetic_field(&mut self, field: MgmSensorValues) {
+        self.external_mag_field = Some(field);
+    }
+
+    fn calculate_current_mgm_tuple(&self, time_ms: u64) -> MgmSensorValues {
+        if SwitchStateBinary::On == self.switch_state {
+            if let Some(ext_field) = self.external_mag_field {
+                return ext_field;
+            }
+            let base_sin_val = 2.0 * PI * FREQUENCY_MGM * (time_ms as f32 / 1000.0);
+            return MgmSensorValues {
+                x: AMPLITUDE_MGM * (base_sin_val + PHASE_X).sin(),
+                y: AMPLITUDE_MGM * (base_sin_val + PHASE_Y).sin(),
+                z: AMPLITUDE_MGM * (base_sin_val + PHASE_Z).sin(),
+            };
+        }
+        MgmSensorValues {
+            x: 0.0,
+            y: 0.0,
+            z: 0.0,
+        }
+    }
+}
+
+impl Model for MagnetometerModel {}
+
+pub struct MagnetorquerModel {
+    switch_state: SwitchStateBinary,
+    torquing: bool,
+    torque_dipole: MgtDipole,
+    pub gen_magnetic_field: Output<MgmSensorValues>,
+    reply_sender: mpsc::Sender<SimReply>,
+}
+
+impl MagnetorquerModel {
+    pub fn new(reply_sender: mpsc::Sender<SimReply>) -> Self {
+        Self {
+            switch_state: SwitchStateBinary::Off,
+            torquing: false,
+            torque_dipole: MgtDipole::default(),
+            gen_magnetic_field: Output::new(),
+            reply_sender,
+        }
+    }
+
+    pub async fn apply_torque(
+        &mut self,
+        duration_and_dipole: (Duration, MgtDipole),
+        scheduler: &Scheduler<Self>,
+    ) {
+        self.torque_dipole = duration_and_dipole.1;
+        self.torquing = true;
+        if scheduler
+            .schedule_event(duration_and_dipole.0, Self::clear_torque, ())
+            .is_err()
+        {
+            log::warn!("torque clearing can only be set for a future time.");
+        }
+        self.generate_magnetic_field(()).await;
+    }
+
+    pub async fn clear_torque(&mut self, _: ()) {
+        self.torque_dipole = MgtDipole::default();
+        self.torquing = false;
+        self.generate_magnetic_field(()).await;
+    }
+
+    pub async fn switch_device(&mut self, switch_state: SwitchStateBinary) {
+        self.switch_state = switch_state;
+        self.generate_magnetic_field(()).await;
+    }
+
+    pub async fn request_housekeeping_data(&mut self, _: (), scheduler: &Scheduler<Self>) {
+        if self.switch_state != SwitchStateBinary::On {
+            return;
+        }
+        scheduler
+            .schedule_event(Duration::from_millis(15), Self::send_housekeeping_data, ())
+            .expect("requesting housekeeping data failed")
+    }
+
+    pub fn send_housekeeping_data(&mut self) {
+        self.reply_sender
+            .send(SimReply::new(MgtReply::Hk(MgtHkSet {
+                dipole: self.torque_dipole,
+                torquing: self.torquing,
+            })))
+            .unwrap();
+    }
+
+    fn calc_magnetic_field(&self, _: MgtDipole) -> MgmSensorValues {
+        // Simplified model: Just returns some fixed magnetic field for now.
+        // Later, we could make this more fancy by incorporating the commanded dipole.
+        MGT_GEN_MAGNETIC_FIELD
+    }
+
+    /// A torquing magnetorquer generates a magnetic field. This function can be used to apply
+    /// the magnetic field.
+    async fn generate_magnetic_field(&mut self, _: ()) {
+        if self.switch_state != SwitchStateBinary::On || !self.torquing {
+            return;
+        }
+        self.gen_magnetic_field
+            .send(self.calc_magnetic_field(self.torque_dipole))
+            .await;
+    }
+}
+
+impl Model for MagnetorquerModel {}
+
+#[cfg(test)]
+pub mod tests {
+    use std::time::Duration;
+
+    use satrs::power::SwitchStateBinary;
+    use satrs_minisim::{
+        acs::{MgmReply, MgmRequest, MgtDipole, MgtHkSet, MgtReply, MgtRequest},
+        eps::PcduSwitch,
+        SerializableSimMsgPayload, SimMessageProvider, SimRequest, SimTarget,
+    };
+
+    use crate::{eps::tests::switch_device_on, test_helpers::SimTestbench};
+
+    #[test]
+    fn test_basic_mgm_request() {
+        let mut sim_testbench = SimTestbench::new();
+        let request = SimRequest::new(MgmRequest::RequestSensorData);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply.is_some());
+        let sim_reply = sim_reply.unwrap();
+        assert_eq!(sim_reply.target(), SimTarget::Mgm);
+        let reply = MgmReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        assert_eq!(reply.switch_state, SwitchStateBinary::Off);
+        assert_eq!(reply.sensor_values.x, 0.0);
+        assert_eq!(reply.sensor_values.y, 0.0);
+        assert_eq!(reply.sensor_values.z, 0.0);
+    }
+
+    #[test]
+    fn test_basic_mgm_request_switched_on() {
+        let mut sim_testbench = SimTestbench::new();
+        switch_device_on(&mut sim_testbench, PcduSwitch::Mgm);
+
+        let mut request = SimRequest::new(MgmRequest::RequestSensorData);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let mut sim_reply_res = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply_res.is_some());
+        let mut sim_reply = sim_reply_res.unwrap();
+        assert_eq!(sim_reply.target(), SimTarget::Mgm);
+        let first_reply = MgmReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        sim_testbench.step_by(Duration::from_millis(50));
+
+        request = SimRequest::new(MgmRequest::RequestSensorData);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        sim_reply_res = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply_res.is_some());
+        sim_reply = sim_reply_res.unwrap();
+
+        let second_reply = MgmReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        // Check that the values are changing.
+        assert!(first_reply != second_reply);
+    }
+
+    #[test]
+    fn test_basic_mgt_request_is_off() {
+        let mut sim_testbench = SimTestbench::new();
+        let request = SimRequest::new(MgtRequest::RequestHk);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply_res = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply_res.is_none());
+    }
+
+    #[test]
+    fn test_basic_mgt_request_is_on() {
+        let mut sim_testbench = SimTestbench::new();
+        switch_device_on(&mut sim_testbench, PcduSwitch::Mgt);
+        let request = SimRequest::new(MgtRequest::RequestHk);
+
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply_res = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply_res.is_some());
+        let sim_reply = sim_reply_res.unwrap();
+        let mgt_reply = MgtReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        match mgt_reply {
+            MgtReply::Hk(hk) => {
+                assert_eq!(hk.dipole, MgtDipole::default());
+                assert!(!hk.torquing);
+            }
+            _ => panic!("unexpected reply"),
+        }
+    }
+
+    fn check_mgt_hk(sim_testbench: &mut SimTestbench, expected_hk_set: MgtHkSet) {
+        let request = SimRequest::new(MgtRequest::RequestHk);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply_res = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply_res.is_some());
+        let sim_reply = sim_reply_res.unwrap();
+        let mgt_reply = MgtReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        match mgt_reply {
+            MgtReply::Hk(hk) => {
+                assert_eq!(hk, expected_hk_set);
+            }
+            _ => panic!("unexpected reply"),
+        }
+    }
+
+    #[test]
+    fn test_basic_mgt_request_is_on_and_torquing() {
+        let mut sim_testbench = SimTestbench::new();
+        switch_device_on(&mut sim_testbench, PcduSwitch::Mgt);
+        let commanded_dipole = MgtDipole {
+            x: -200,
+            y: 200,
+            z: 1000,
+        };
+        let request = SimRequest::new(MgtRequest::ApplyTorque {
+            duration: Duration::from_millis(100),
+            dipole: commanded_dipole,
+        });
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step_by(Duration::from_millis(5));
+
+        check_mgt_hk(
+            &mut sim_testbench,
+            MgtHkSet {
+                dipole: commanded_dipole,
+                torquing: true,
+            },
+        );
+        sim_testbench.step_by(Duration::from_millis(100));
+        check_mgt_hk(
+            &mut sim_testbench,
+            MgtHkSet {
+                dipole: MgtDipole::default(),
+                torquing: false,
+            },
+        );
+    }
+}

satrs-minisim/src/controller.rs

@@ -0,0 +1,189 @@
+use std::{sync::mpsc, time::Duration};
+
+use asynchronix::{
+    simulation::{Address, Simulation},
+    time::{Clock, MonotonicTime, SystemClock},
+};
+use satrs_minisim::{
+    acs::{MgmRequest, MgtRequest},
+    eps::PcduRequest,
+    SerializableSimMsgPayload, SimCtrlReply, SimCtrlRequest, SimMessageProvider, SimReply,
+    SimRequest, SimRequestError, SimTarget,
+};
+
+use crate::{
+    acs::{MagnetometerModel, MagnetorquerModel},
+    eps::PcduModel,
+};
+
+// The simulation controller processes requests and drives the simulation.
+pub struct SimController {
+    pub sys_clock: SystemClock,
+    pub request_receiver: mpsc::Receiver<SimRequest>,
+    pub reply_sender: mpsc::Sender<SimReply>,
+    pub simulation: Simulation,
+    pub mgm_addr: Address<MagnetometerModel>,
+    pub pcdu_addr: Address<PcduModel>,
+    pub mgt_addr: Address<MagnetorquerModel>,
+}
+
+impl SimController {
+    pub fn new(
+        sys_clock: SystemClock,
+        request_receiver: mpsc::Receiver<SimRequest>,
+        reply_sender: mpsc::Sender<SimReply>,
+        simulation: Simulation,
+        mgm_addr: Address<MagnetometerModel>,
+        pcdu_addr: Address<PcduModel>,
+        mgt_addr: Address<MagnetorquerModel>,
+    ) -> Self {
+        Self {
+            sys_clock,
+            request_receiver,
+            reply_sender,
+            simulation,
+            mgm_addr,
+            pcdu_addr,
+            mgt_addr,
+        }
+    }
+
+    pub fn run(&mut self, start_time: MonotonicTime, udp_polling_interval_ms: u64) {
+        let mut t = start_time + Duration::from_millis(udp_polling_interval_ms);
+        self.sys_clock.synchronize(t);
+        loop {
+            // Check for UDP requests every millisecond. Shift the simulator ahead here to prevent
+            // replies lying in the past.
+            t += Duration::from_millis(udp_polling_interval_ms);
+            self.simulation
+                .step_until(t)
+                .expect("simulation step failed");
+            self.handle_sim_requests();
+
+            self.sys_clock.synchronize(t);
+        }
+    }
+
+    pub fn handle_sim_requests(&mut self) {
+        loop {
+            match self.request_receiver.try_recv() {
+                Ok(request) => {
+                    if let Err(e) = match request.target() {
+                        SimTarget::SimCtrl => self.handle_ctrl_request(&request),
+                        SimTarget::Mgm => self.handle_mgm_request(&request),
+                        SimTarget::Mgt => self.handle_mgt_request(&request),
+                        SimTarget::Pcdu => self.handle_pcdu_request(&request),
+                    } {
+                        self.handle_invalid_request_with_valid_target(e, &request)
+                    }
+                }
+                Err(e) => match e {
+                    mpsc::TryRecvError::Empty => break,
+                    mpsc::TryRecvError::Disconnected => {
+                        panic!("all request sender disconnected")
+                    }
+                },
+            }
+        }
+    }
+
+    fn handle_ctrl_request(&mut self, request: &SimRequest) -> Result<(), SimRequestError> {
+        let sim_ctrl_request = SimCtrlRequest::from_sim_message(request)?;
+        match sim_ctrl_request {
+            SimCtrlRequest::Ping => {
+                self.reply_sender
+                    .send(SimReply::new(SimCtrlReply::Pong))
+                    .expect("sending reply from sim controller failed");
+            }
+        }
+        Ok(())
+    }
+    fn handle_mgm_request(&mut self, request: &SimRequest) -> Result<(), SimRequestError> {
+        let mgm_request = MgmRequest::from_sim_message(request)?;
+        match mgm_request {
+            MgmRequest::RequestSensorData => {
+                self.simulation.send_event(
+                    MagnetometerModel::send_sensor_values,
+                    (),
+                    &self.mgm_addr,
+                );
+            }
+        }
+        Ok(())
+    }
+
+    fn handle_pcdu_request(&mut self, request: &SimRequest) -> Result<(), SimRequestError> {
+        let pcdu_request = PcduRequest::from_sim_message(request)?;
+        match pcdu_request {
+            PcduRequest::RequestSwitchInfo => {
+                self.simulation
+                    .send_event(PcduModel::request_switch_info, (), &self.pcdu_addr);
+            }
+            PcduRequest::SwitchDevice { switch, state } => {
+                self.simulation.send_event(
+                    PcduModel::switch_device,
+                    (switch, state),
+                    &self.pcdu_addr,
+                );
+            }
+        }
+        Ok(())
+    }
+
+    fn handle_mgt_request(&mut self, request: &SimRequest) -> Result<(), SimRequestError> {
+        let mgt_request = MgtRequest::from_sim_message(request)?;
+        match mgt_request {
+            MgtRequest::ApplyTorque { duration, dipole } => self.simulation.send_event(
+                MagnetorquerModel::apply_torque,
+                (duration, dipole),
+                &self.mgt_addr,
+            ),
+            MgtRequest::RequestHk => self.simulation.send_event(
+                MagnetorquerModel::request_housekeeping_data,
+                (),
+                &self.mgt_addr,
+            ),
+        }
+        Ok(())
+    }
+
+    fn handle_invalid_request_with_valid_target(
+        &self,
+        error: SimRequestError,
+        request: &SimRequest,
+    ) {
+        log::warn!(
+            "received invalid {:?} request: {:?}",
+            request.target(),
+            error
+        );
+        self.reply_sender
+            .send(SimReply::new(SimCtrlReply::from(error)))
+            .expect("sending reply from sim controller failed");
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test_helpers::SimTestbench;
+
+    use super::*;
+
+    #[test]
+    fn test_basic_ping() {
+        let mut sim_testbench = SimTestbench::new();
+        let request = SimRequest::new(SimCtrlRequest::Ping);
+        sim_testbench
+            .send_request(request)
+            .expect("sending sim ctrl request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply.is_some());
+        let sim_reply = sim_reply.unwrap();
+        assert_eq!(sim_reply.target(), SimTarget::SimCtrl);
+        let reply = SimCtrlReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize MGM sensor values");
+        assert_eq!(reply, SimCtrlReply::Pong);
+    }
+}

satrs-minisim/src/eps.rs

@@ -0,0 +1,185 @@
+use std::{collections::HashMap, sync::mpsc, time::Duration};
+
+use asynchronix::{
+    model::{Model, Output},
+    time::Scheduler,
+};
+use satrs::power::SwitchStateBinary;
+use satrs_minisim::{
+    eps::{PcduReply, PcduSwitch, SwitchMap},
+    SimReply,
+};
+
+pub const SWITCH_INFO_DELAY_MS: u64 = 10;
+
+pub struct PcduModel {
+    pub switcher_map: SwitchMap,
+    pub mgm_switch: Output<SwitchStateBinary>,
+    pub mgt_switch: Output<SwitchStateBinary>,
+    pub reply_sender: mpsc::Sender<SimReply>,
+}
+
+impl PcduModel {
+    pub fn new(reply_sender: mpsc::Sender<SimReply>) -> Self {
+        let mut switcher_map = HashMap::new();
+        switcher_map.insert(PcduSwitch::Mgm, SwitchStateBinary::Off);
+        switcher_map.insert(PcduSwitch::Mgt, SwitchStateBinary::Off);
+
+        Self {
+            switcher_map,
+            mgm_switch: Output::new(),
+            mgt_switch: Output::new(),
+            reply_sender,
+        }
+    }
+
+    pub async fn request_switch_info(&mut self, _: (), scheduler: &Scheduler<Self>) {
+        scheduler
+            .schedule_event(
+                Duration::from_millis(SWITCH_INFO_DELAY_MS),
+                Self::send_switch_info,
+                (),
+            )
+            .expect("requesting switch info failed");
+    }
+
+    pub fn send_switch_info(&mut self) {
+        let reply = SimReply::new(PcduReply::SwitchInfo(self.switcher_map.clone()));
+        self.reply_sender.send(reply).unwrap();
+    }
+
+    pub async fn switch_device(
+        &mut self,
+        switch_and_target_state: (PcduSwitch, SwitchStateBinary),
+    ) {
+        let val = self
+            .switcher_map
+            .get_mut(&switch_and_target_state.0)
+            .unwrap_or_else(|| panic!("switch {:?} not found", switch_and_target_state.0));
+        *val = switch_and_target_state.1;
+        match switch_and_target_state.0 {
+            PcduSwitch::Mgm => {
+                self.mgm_switch.send(switch_and_target_state.1).await;
+            }
+            PcduSwitch::Mgt => {
+                self.mgt_switch.send(switch_and_target_state.1).await;
+            }
+        }
+    }
+}
+
+impl Model for PcduModel {}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    use satrs_minisim::{
+        eps::PcduRequest, SerializableSimMsgPayload, SimMessageProvider, SimRequest, SimTarget,
+    };
+
+    use crate::test_helpers::SimTestbench;
+
+    fn switch_device(
+        sim_testbench: &mut SimTestbench,
+        switch: PcduSwitch,
+        target: SwitchStateBinary,
+    ) {
+        let request = SimRequest::new(PcduRequest::SwitchDevice {
+            switch,
+            state: target,
+        });
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM switch request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+    }
+
+    #[allow(dead_code)]
+    pub(crate) fn switch_device_off(sim_testbench: &mut SimTestbench, switch: PcduSwitch) {
+        switch_device(sim_testbench, switch, SwitchStateBinary::Off);
+    }
+    pub(crate) fn switch_device_on(sim_testbench: &mut SimTestbench, switch: PcduSwitch) {
+        switch_device(sim_testbench, switch, SwitchStateBinary::On);
+    }
+
+    pub(crate) fn get_all_off_switch_map() -> SwitchMap {
+        let mut switcher_map = SwitchMap::new();
+        switcher_map.insert(super::PcduSwitch::Mgm, super::SwitchStateBinary::Off);
+        switcher_map.insert(super::PcduSwitch::Mgt, super::SwitchStateBinary::Off);
+        switcher_map
+    }
+
+    fn check_switch_state(sim_testbench: &mut SimTestbench, expected_switch_map: &SwitchMap) {
+        let request = SimRequest::new(PcduRequest::RequestSwitchInfo);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step();
+        let sim_reply = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply.is_some());
+        let sim_reply = sim_reply.unwrap();
+        assert_eq!(sim_reply.target(), SimTarget::Pcdu);
+        let pcdu_reply = PcduReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize PCDU switch info");
+        match pcdu_reply {
+            PcduReply::SwitchInfo(switch_map) => {
+                assert_eq!(switch_map, *expected_switch_map);
+            }
+        }
+    }
+
+    fn test_pcdu_switching_single_switch(switch: PcduSwitch, target: SwitchStateBinary) {
+        let mut sim_testbench = SimTestbench::new();
+        switch_device(&mut sim_testbench, switch, target);
+        let mut switcher_map = get_all_off_switch_map();
+        *switcher_map.get_mut(&switch).unwrap() = target;
+        check_switch_state(&mut sim_testbench, &switcher_map);
+    }
+
+    #[test]
+    fn test_pcdu_switcher_request() {
+        let mut sim_testbench = SimTestbench::new();
+        let request = SimRequest::new(PcduRequest::RequestSwitchInfo);
+        sim_testbench
+            .send_request(request)
+            .expect("sending MGM request failed");
+        sim_testbench.handle_sim_requests();
+        sim_testbench.step_by(Duration::from_millis(1));
+
+        let sim_reply = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply.is_none());
+        // Reply takes 20ms
+        sim_testbench.step_by(Duration::from_millis(25));
+        let sim_reply = sim_testbench.try_receive_next_reply();
+        assert!(sim_reply.is_some());
+        let sim_reply = sim_reply.unwrap();
+        assert_eq!(sim_reply.target(), SimTarget::Pcdu);
+        let pcdu_reply = PcduReply::from_sim_message(&sim_reply)
+            .expect("failed to deserialize PCDU switch info");
+        match pcdu_reply {
+            PcduReply::SwitchInfo(switch_map) => {
+                assert_eq!(switch_map, get_all_off_switch_map());
+            }
+        }
+    }
+
+    #[test]
+    fn test_pcdu_switching_mgm_on() {
+        test_pcdu_switching_single_switch(PcduSwitch::Mgm, SwitchStateBinary::On);
+    }
+
+    #[test]
+    fn test_pcdu_switching_mgt_on() {
+        test_pcdu_switching_single_switch(PcduSwitch::Mgt, SwitchStateBinary::On);
+    }
+
+    #[test]
+    fn test_pcdu_switching_mgt_off() {
+        test_pcdu_switching_single_switch(PcduSwitch::Mgt, SwitchStateBinary::On);
+        test_pcdu_switching_single_switch(PcduSwitch::Mgt, SwitchStateBinary::Off);
+    }
+}

satrs-minisim/src/lib.rs

@@ -0,0 +1,383 @@
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SimTarget {
+    SimCtrl,
+    Mgm,
+    Mgt,
+    Pcdu,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SimMessage {
+    pub target: SimTarget,
+    pub payload: String,
+}
+
+/// A generic simulation request type. Right now, the payload data is expected to be
+/// JSON, which might be changed in the future.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SimRequest {
+    inner: SimMessage,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SimMessageType {
+    Request,
+    Reply,
+}
+
+/// Generic trait implemented by simulation request or reply payloads. It ties the request or
+/// reply to a specific target and provides an API which does boilerplate tasks like checking the
+/// validity of the target.
+pub trait SerializableSimMsgPayload<P: SimMessageProvider>:
+    Serialize + DeserializeOwned + Sized
+{
+    const TARGET: SimTarget;
+
+    fn from_sim_message(sim_message: &P) -> Result<Self, SimMessageError<P>> {
+        if sim_message.target() == Self::TARGET {
+            return Ok(serde_json::from_str(sim_message.payload())?);
+        }
+        Err(SimMessageError::TargetRequestMissmatch(sim_message.clone()))
+    }
+}
+
+pub trait SimMessageProvider: Serialize + DeserializeOwned + Clone + Sized {
+    fn msg_type(&self) -> SimMessageType;
+    fn target(&self) -> SimTarget;
+    fn payload(&self) -> &String;
+    fn from_raw_data(data: &[u8]) -> serde_json::Result<Self> {
+        serde_json::from_slice(data)
+    }
+}
+
+impl SimRequest {
+    pub fn new<T: SerializableSimMsgPayload<SimRequest>>(serializable_request: T) -> Self {
+        Self {
+            inner: SimMessage {
+                target: T::TARGET,
+                payload: serde_json::to_string(&serializable_request).unwrap(),
+            },
+        }
+    }
+}
+
+impl SimMessageProvider for SimRequest {
+    fn target(&self) -> SimTarget {
+        self.inner.target
+    }
+    fn payload(&self) -> &String {
+        &self.inner.payload
+    }
+
+    fn msg_type(&self) -> SimMessageType {
+        SimMessageType::Request
+    }
+}
+
+/// A generic simulation reply type. Right now, the payload data is expected to be
+/// JSON, which might be changed inthe future.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SimReply {
+    inner: SimMessage,
+}
+
+impl SimReply {
+    pub fn new<T: SerializableSimMsgPayload<SimReply>>(serializable_reply: T) -> Self {
+        Self {
+            inner: SimMessage {
+                target: T::TARGET,
+                payload: serde_json::to_string(&serializable_reply).unwrap(),
+            },
+        }
+    }
+}
+
+impl SimMessageProvider for SimReply {
+    fn target(&self) -> SimTarget {
+        self.inner.target
+    }
+    fn payload(&self) -> &String {
+        &self.inner.payload
+    }
+    fn msg_type(&self) -> SimMessageType {
+        SimMessageType::Reply
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SimCtrlRequest {
+    Ping,
+}
+
+impl SerializableSimMsgPayload<SimRequest> for SimCtrlRequest {
+    const TARGET: SimTarget = SimTarget::SimCtrl;
+}
+
+pub type SimReplyError = SimMessageError<SimReply>;
+pub type SimRequestError = SimMessageError<SimRequest>;
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SimMessageError<P> {
+    SerdeJson(String),
+    TargetRequestMissmatch(P),
+}
+
+impl<P> From<serde_json::Error> for SimMessageError<P> {
+    fn from(error: serde_json::Error) -> SimMessageError<P> {
+        SimMessageError::SerdeJson(error.to_string())
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SimCtrlReply {
+    Pong,
+    InvalidRequest(SimRequestError),
+}
+
+impl SerializableSimMsgPayload<SimReply> for SimCtrlReply {
+    const TARGET: SimTarget = SimTarget::SimCtrl;
+}
+
+impl From<SimRequestError> for SimCtrlReply {
+    fn from(error: SimRequestError) -> Self {
+        SimCtrlReply::InvalidRequest(error)
+    }
+}
+
+pub mod eps {
+    use super::*;
+    use std::collections::HashMap;
+
+    use satrs::power::SwitchStateBinary;
+
+    pub type SwitchMap = HashMap<PcduSwitch, SwitchStateBinary>;
+
+    #[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize, Hash)]
+    pub enum PcduSwitch {
+        Mgm = 0,
+        Mgt = 1,
+    }
+
+    #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
+    pub enum PcduRequest {
+        SwitchDevice {
+            switch: PcduSwitch,
+            state: SwitchStateBinary,
+        },
+        RequestSwitchInfo,
+    }
+
+    impl SerializableSimMsgPayload<SimRequest> for PcduRequest {
+        const TARGET: SimTarget = SimTarget::Pcdu;
+    }
+
+    #[derive(Debug, Clone, Serialize, Deserialize)]
+    pub enum PcduReply {
+        SwitchInfo(SwitchMap),
+    }
+
+    impl SerializableSimMsgPayload<SimReply> for PcduReply {
+        const TARGET: SimTarget = SimTarget::Pcdu;
+    }
+}
+
+pub mod acs {
+    use std::time::Duration;
+
+    use satrs::power::SwitchStateBinary;
+
+    use super::*;
+
+    #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
+    pub enum MgmRequest {
+        RequestSensorData,
+    }
+
+    impl SerializableSimMsgPayload<SimRequest> for MgmRequest {
+        const TARGET: SimTarget = SimTarget::Mgm;
+    }
+
+    // Normally, small magnetometers generate their output as a signed 16 bit raw format or something
+    // similar which needs to be converted to a signed float value with physical units. We will
+    // simplify this now and generate the signed float values directly.
+    #[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
+    pub struct MgmSensorValues {
+        pub x: f32,
+        pub y: f32,
+        pub z: f32,
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
+    pub struct MgmReply {
+        pub switch_state: SwitchStateBinary,
+        pub sensor_values: MgmSensorValues,
+    }
+
+    impl SerializableSimMsgPayload<SimReply> for MgmReply {
+        const TARGET: SimTarget = SimTarget::Mgm;
+    }
+
+    pub const MGT_GEN_MAGNETIC_FIELD: MgmSensorValues = MgmSensorValues {
+        x: 0.03,
+        y: -0.03,
+        z: 0.03,
+    };
+
+    // Simple model using i16 values.
+    #[derive(Default, Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+    pub struct MgtDipole {
+        pub x: i16,
+        pub y: i16,
+        pub z: i16,
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
+    pub enum MgtRequestType {
+        ApplyTorque,
+    }
+
+    #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
+    pub enum MgtRequest {
+        ApplyTorque {
+            duration: Duration,
+            dipole: MgtDipole,
+        },
+        RequestHk,
+    }
+
+    impl SerializableSimMsgPayload<SimRequest> for MgtRequest {
+        const TARGET: SimTarget = SimTarget::Mgt;
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+    pub struct MgtHkSet {
+        pub dipole: MgtDipole,
+        pub torquing: bool,
+    }
+
+    #[derive(Debug, Copy, Clone, Serialize, Deserialize)]
+    pub enum MgtReply {
+        Ack(MgtRequestType),
+        Nak(MgtRequestType),
+        Hk(MgtHkSet),
+    }
+
+    impl SerializableSimMsgPayload<SimReply> for MgtReply {
+        const TARGET: SimTarget = SimTarget::Mgm;
+    }
+}
+
+pub mod udp {
+    use std::{
+        net::{SocketAddr, UdpSocket},
+        time::Duration,
+    };
+
+    use thiserror::Error;
+
+    use crate::{SimReply, SimRequest};
+
+    #[derive(Error, Debug)]
+    pub enum ReceptionError {
+        #[error("IO error: {0}")]
+        Io(#[from] std::io::Error),
+        #[error("Serde JSON error: {0}")]
+        SerdeJson(#[from] serde_json::Error),
+    }
+
+    pub struct SimUdpClient {
+        socket: UdpSocket,
+        pub reply_buf: [u8; 4096],
+    }
+
+    impl SimUdpClient {
+        pub fn new(
+            server_addr: &SocketAddr,
+            non_blocking: bool,
+            read_timeot_ms: Option<u64>,
+        ) -> std::io::Result<Self> {
+            let socket = UdpSocket::bind("127.0.0.1:0")?;
+            socket.set_nonblocking(non_blocking)?;
+            socket
+                .connect(server_addr)
+                .expect("could not connect to server addr");
+            if let Some(read_timeout) = read_timeot_ms {
+                // Set a read timeout so the test does not hang on failures.
+                socket.set_read_timeout(Some(Duration::from_millis(read_timeout)))?;
+            }
+            Ok(Self {
+                socket,
+                reply_buf: [0; 4096],
+            })
+        }
+
+        pub fn set_nonblocking(&self, non_blocking: bool) -> std::io::Result<()> {
+            self.socket.set_nonblocking(non_blocking)
+        }
+
+        pub fn set_read_timeout(&self, read_timeout_ms: u64) -> std::io::Result<()> {
+            self.socket
+                .set_read_timeout(Some(Duration::from_millis(read_timeout_ms)))
+        }
+
+        pub fn send_request(&self, sim_request: &SimRequest) -> std::io::Result<usize> {
+            self.socket.send(
+                &serde_json::to_vec(sim_request).expect("conversion of request to vector failed"),
+            )
+        }
+
+        pub fn recv_raw(&mut self) -> std::io::Result<usize> {
+            self.socket.recv(&mut self.reply_buf)
+        }
+
+        pub fn recv_sim_reply(&mut self) -> Result<SimReply, ReceptionError> {
+            let read_len = self.recv_raw()?;
+            Ok(serde_json::from_slice(&self.reply_buf[0..read_len])?)
+        }
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+
+    #[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+    pub enum DummyRequest {
+        Ping,
+    }
+
+    impl SerializableSimMsgPayload<SimRequest> for DummyRequest {
+        const TARGET: SimTarget = SimTarget::SimCtrl;
+    }
+
+    #[derive(Debug, Copy, Clone, PartialEq, Eq, Serialize, Deserialize)]
+    pub enum DummyReply {
+        Pong,
+    }
+
+    impl SerializableSimMsgPayload<SimReply> for DummyReply {
+        const TARGET: SimTarget = SimTarget::SimCtrl;
+    }
+
+    #[test]
+    fn test_basic_request() {
+        let sim_request = SimRequest::new(DummyRequest::Ping);
+        assert_eq!(sim_request.target(), SimTarget::SimCtrl);
+        assert_eq!(sim_request.msg_type(), SimMessageType::Request);
+        let dummy_request =
+            DummyRequest::from_sim_message(&sim_request).expect("deserialization failed");
+        assert_eq!(dummy_request, DummyRequest::Ping);
+    }
+
+    #[test]
+    fn test_basic_reply() {
+        let sim_reply = SimReply::new(DummyReply::Pong);
+        assert_eq!(sim_reply.target(), SimTarget::SimCtrl);
+        assert_eq!(sim_reply.msg_type(), SimMessageType::Reply);
+        let dummy_request =
+            DummyReply::from_sim_message(&sim_reply).expect("deserialization failed");
+        assert_eq!(dummy_request, DummyReply::Pong);
+    }
+}

satrs-minisim/src/main.rs

@@ -0,0 +1,103 @@
+use acs::{MagnetometerModel, MagnetorquerModel};
+use asynchronix::simulation::{Mailbox, SimInit};
+use asynchronix::time::{MonotonicTime, SystemClock};
+use controller::SimController;
+use eps::PcduModel;
+use satrs_minisim::{SimReply, SimRequest};
+use std::sync::mpsc;
+use std::thread;
+use std::time::{Duration, SystemTime};
+use udp::SimUdpServer;
+
+mod acs;
+mod controller;
+mod eps;
+#[cfg(test)]
+mod test_helpers;
+mod time;
+mod udp;
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum ThreadingModel {
+    Default = 0,
+    Single = 1,
+}
+
+fn create_sim_controller(
+    threading_model: ThreadingModel,
+    start_time: MonotonicTime,
+    reply_sender: mpsc::Sender<SimReply>,
+    request_receiver: mpsc::Receiver<SimRequest>,
+) -> SimController {
+    // Instantiate models and their mailboxes.
+    let mgm_model = MagnetometerModel::new(Duration::from_millis(50), reply_sender.clone());
+
+    let mgm_mailbox = Mailbox::new();
+    let mgm_addr = mgm_mailbox.address();
+    let pcdu_mailbox = Mailbox::new();
+    let pcdu_addr = pcdu_mailbox.address();
+    let mgt_mailbox = Mailbox::new();
+    let mgt_addr = mgt_mailbox.address();
+
+    let mut pcdu_model = PcduModel::new(reply_sender.clone());
+    pcdu_model
+        .mgm_switch
+        .connect(MagnetometerModel::switch_device, &mgm_addr);
+
+    let mut mgt_model = MagnetorquerModel::new(reply_sender.clone());
+    // Input connections.
+    pcdu_model
+        .mgt_switch
+        .connect(MagnetorquerModel::switch_device, &mgt_addr);
+    // Output connections.
+    mgt_model
+        .gen_magnetic_field
+        .connect(MagnetometerModel::apply_external_magnetic_field, &mgm_addr);
+
+    // Instantiate the simulator
+    let sys_clock = SystemClock::from_system_time(start_time, SystemTime::now());
+    let sim_init = if threading_model == ThreadingModel::Single {
+        SimInit::with_num_threads(1)
+    } else {
+        SimInit::new()
+    };
+    let simulation = sim_init
+        .add_model(mgm_model, mgm_mailbox)
+        .add_model(pcdu_model, pcdu_mailbox)
+        .add_model(mgt_model, mgt_mailbox)
+        .init(start_time);
+    SimController::new(
+        sys_clock,
+        request_receiver,
+        reply_sender,
+        simulation,
+        mgm_addr,
+        pcdu_addr,
+        mgt_addr,
+    )
+}
+
+fn main() {
+    let (request_sender, request_receiver) = mpsc::channel();
+    let (reply_sender, reply_receiver) = mpsc::channel();
+    let t0 = MonotonicTime::EPOCH;
+    let mut sim_ctrl =
+        create_sim_controller(ThreadingModel::Default, t0, reply_sender, request_receiver);
+
+    // This thread schedules the simulator.
+    let sim_thread = thread::spawn(move || {
+        sim_ctrl.run(t0, 1);
+    });
+
+    let mut udp_server = SimUdpServer::new(0, request_sender, reply_receiver, 200, None)
+        .expect("could not create UDP request server");
+    // This thread manages the simulator UDP server.
+    let udp_tc_thread = thread::spawn(move || {
+        udp_server.run();
+    });
+
+    sim_thread.join().expect("joining simulation thread failed");
+    udp_tc_thread
+        .join()
+        .expect("joining UDP server thread failed");
+}

satrs-minisim/src/test_helpers.rs

@@ -0,0 +1,56 @@
+use delegate::delegate;
+use std::{sync::mpsc, time::Duration};
+
+use asynchronix::time::MonotonicTime;
+use satrs_minisim::{SimReply, SimRequest};
+
+use crate::{controller::SimController, create_sim_controller, ThreadingModel};
+
+pub struct SimTestbench {
+    pub sim_controller: SimController,
+    pub reply_receiver: mpsc::Receiver<SimReply>,
+    pub request_sender: mpsc::Sender<SimRequest>,
+}
+
+impl SimTestbench {
+    pub fn new() -> Self {
+        let (request_sender, request_receiver) = mpsc::channel();
+        let (reply_sender, reply_receiver) = mpsc::channel();
+        let t0 = MonotonicTime::EPOCH;
+        let sim_ctrl =
+            create_sim_controller(ThreadingModel::Single, t0, reply_sender, request_receiver);
+
+        Self {
+            sim_controller: sim_ctrl,
+            reply_receiver,
+            request_sender,
+        }
+    }
+
+    delegate! {
+        to self.sim_controller {
+            pub fn handle_sim_requests(&mut self);
+        }
+        to self.sim_controller.simulation {
+            pub fn step(&mut self);
+            pub fn step_by(&mut self, duration: Duration);
+        }
+    }
+
+    pub fn send_request(&self, request: SimRequest) -> Result<(), mpsc::SendError<SimRequest>> {
+        self.request_sender.send(request)
+    }
+
+    pub fn try_receive_next_reply(&self) -> Option<SimReply> {
+        match self.reply_receiver.try_recv() {
+            Ok(reply) => Some(reply),
+            Err(e) => {
+                if e == mpsc::TryRecvError::Empty {
+                    None
+                } else {
+                    panic!("reply_receiver disconnected");
+                }
+            }
+        }
+    }
+}

satrs-minisim/src/time.rs

@@ -0,0 +1,5 @@
+use asynchronix::time::MonotonicTime;
+
+pub fn current_millis(time: MonotonicTime) -> u64 {
+    (time.as_secs() as u64 * 1000) + (time.subsec_nanos() as u64 / 1_000_000)
+}

satrs-minisim/src/udp.rs

@@ -0,0 +1,390 @@
+use std::{
+    collections::VecDeque,
+    io::ErrorKind,
+    net::{SocketAddr, UdpSocket},
+    sync::{atomic::AtomicBool, mpsc, Arc},
+    time::Duration,
+};
+
+use satrs_minisim::{SimMessageProvider, SimReply, SimRequest};
+
+// A UDP server which handles all TC received by a client application.
+pub struct SimUdpServer {
+    socket: UdpSocket,
+    request_sender: mpsc::Sender<SimRequest>,
+    // shared_last_sender: SharedSocketAddr,
+    reply_receiver: mpsc::Receiver<SimReply>,
+    reply_queue: VecDeque<SimReply>,
+    max_num_replies: usize,
+    // Stop signal to stop the server. Required for unittests and useful to allow clean shutdown
+    // of the application.
+    stop_signal: Option<Arc<AtomicBool>>,
+    idle_sleep_period_ms: u64,
+    req_buf: [u8; 4096],
+    sender_addr: Option<SocketAddr>,
+}
+
+impl SimUdpServer {
+    pub fn new(
+        local_port: u16,
+        request_sender: mpsc::Sender<SimRequest>,
+        reply_receiver: mpsc::Receiver<SimReply>,
+        max_num_replies: usize,
+        stop_signal: Option<Arc<AtomicBool>>,
+    ) -> std::io::Result<Self> {
+        let socket = UdpSocket::bind(SocketAddr::from(([0, 0, 0, 0], local_port)))?;
+        socket.set_nonblocking(true)?;
+        Ok(Self {
+            socket,
+            request_sender,
+            reply_receiver,
+            reply_queue: VecDeque::new(),
+            max_num_replies,
+            stop_signal,
+            idle_sleep_period_ms: 3,
+            req_buf: [0; 4096],
+            sender_addr: None,
+        })
+    }
+
+    #[allow(dead_code)]
+    pub fn server_addr(&self) -> std::io::Result<SocketAddr> {
+        self.socket.local_addr()
+    }
+
+    pub fn run(&mut self) {
+        loop {
+            if let Some(stop_signal) = &self.stop_signal {
+                if stop_signal.load(std::sync::atomic::Ordering::Relaxed) {
+                    break;
+                }
+            }
+            let processed_requests = self.process_requests();
+            let processed_replies = self.process_replies();
+            let sent_replies = self.send_replies();
+            // Sleep for a bit if there is nothing to do to prevent burning CPU cycles. Delay
+            // should be kept short to ensure responsiveness of the system.
+            if !processed_requests && !processed_replies && !sent_replies {
+                std::thread::sleep(Duration::from_millis(self.idle_sleep_period_ms));
+            }
+        }
+    }
+
+    fn process_requests(&mut self) -> bool {
+        let mut processed_requests = false;
+        loop {
+            // Blocks for a certain amount of time until data is received to allow doing periodic
+            // work like checking the stop signal.
+            let (bytes_read, src) = match self.socket.recv_from(&mut self.req_buf) {
+                Ok((bytes_read, src)) => (bytes_read, src),
+                Err(e) if e.kind() == ErrorKind::WouldBlock => {
+                    // Continue to perform regular checks like the stop signal.
+                    break;
+                }
+                Err(e) => {
+                    // Handle unexpected errors (e.g., socket closed) here.
+                    log::error!("unexpected request server error: {e}");
+                    break;
+                }
+            };
+
+            self.sender_addr = Some(src);
+
+            let sim_req = SimRequest::from_raw_data(&self.req_buf[..bytes_read]);
+            if sim_req.is_err() {
+                log::warn!(
+                    "received UDP request with invalid format: {}",
+                    sim_req.unwrap_err()
+                );
+                return processed_requests;
+            }
+            self.request_sender.send(sim_req.unwrap()).unwrap();
+            processed_requests = true;
+        }
+        processed_requests
+    }
+
+    fn process_replies(&mut self) -> bool {
+        let mut processed_replies = false;
+        loop {
+            match self.reply_receiver.try_recv() {
+                Ok(reply) => {
+                    if self.reply_queue.len() >= self.max_num_replies {
+                        self.reply_queue.pop_front();
+                    }
+                    self.reply_queue.push_back(reply);
+                    processed_replies = true;
+                }
+                Err(e) => match e {
+                    mpsc::TryRecvError::Empty => return processed_replies,
+                    mpsc::TryRecvError::Disconnected => {
+                        log::error!("all UDP reply senders disconnected")
+                    }
+                },
+            }
+        }
+    }
+
+    fn send_replies(&mut self) -> bool {
+        if self.sender_addr.is_none() {
+            return false;
+        }
+        let mut sent_replies = false;
+        while !self.reply_queue.is_empty() {
+            let next_reply_to_send = self.reply_queue.pop_front().unwrap();
+            self.socket
+                .send_to(
+                    serde_json::to_string(&next_reply_to_send)
+                        .unwrap()
+                        .as_bytes(),
+                    self.sender_addr.unwrap(),
+                )
+                .expect("sending reply failed");
+            sent_replies = true;
+        }
+        sent_replies
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{
+        io::ErrorKind,
+        sync::{
+            atomic::{AtomicBool, Ordering},
+            mpsc, Arc,
+        },
+        time::Duration,
+    };
+
+    use satrs_minisim::{
+        eps::{PcduReply, PcduRequest},
+        udp::{ReceptionError, SimUdpClient},
+        SimCtrlReply, SimCtrlRequest, SimReply, SimRequest,
+    };
+
+    use crate::eps::tests::get_all_off_switch_map;
+    use delegate::delegate;
+
+    use super::SimUdpServer;
+
+    // Wait time to ensure even possibly laggy systems like CI servers can run the tests.
+    const SERVER_WAIT_TIME_MS: u64 = 50;
+
+    struct UdpTestbench {
+        client: SimUdpClient,
+        stop_signal: Arc<AtomicBool>,
+        request_receiver: mpsc::Receiver<SimRequest>,
+        reply_sender: mpsc::Sender<SimReply>,
+    }
+
+    impl UdpTestbench {
+        pub fn new(
+            client_non_blocking: bool,
+            client_read_timeout_ms: Option<u64>,
+            max_num_replies: usize,
+        ) -> std::io::Result<(Self, SimUdpServer)> {
+            let (request_sender, request_receiver) = mpsc::channel();
+            let (reply_sender, reply_receiver) = mpsc::channel();
+            let stop_signal = Arc::new(AtomicBool::new(false));
+            let server = SimUdpServer::new(
+                0,
+                request_sender,
+                reply_receiver,
+                max_num_replies,
+                Some(stop_signal.clone()),
+            )?;
+            let server_addr = server.server_addr()?;
+            Ok((
+                Self {
+                    client: SimUdpClient::new(
+                        &server_addr,
+                        client_non_blocking,
+                        client_read_timeout_ms,
+                    )?,
+                    stop_signal,
+                    request_receiver,
+                    reply_sender,
+                },
+                server,
+            ))
+        }
+
+        pub fn try_recv_request(&self) -> Result<SimRequest, mpsc::TryRecvError> {
+            self.request_receiver.try_recv()
+        }
+
+        pub fn stop(&self) {
+            self.stop_signal.store(true, Ordering::Relaxed);
+        }
+
+        pub fn send_reply(&self, sim_reply: &SimReply) {
+            self.reply_sender
+                .send(sim_reply.clone())
+                .expect("sending sim reply failed");
+        }
+
+        delegate! {
+            to self.client {
+                pub fn send_request(&self, sim_request: &SimRequest) -> std::io::Result<usize>;
+                pub fn recv_sim_reply(&mut self) -> Result<SimReply, ReceptionError>;
+            }
+        }
+
+        pub fn check_no_sim_reply_available(&mut self) {
+            if let Err(ReceptionError::Io(ref io_error)) = self.recv_sim_reply() {
+                if io_error.kind() == ErrorKind::WouldBlock {
+                    // Continue to perform regular checks like the stop signal.
+                    return;
+                } else {
+                    // Handle unexpected errors (e.g., socket closed) here.
+                    panic!("unexpected request server error: {io_error}");
+                }
+            }
+            panic!("unexpected reply available");
+        }
+
+        pub fn check_next_sim_reply(&mut self, expected_reply: &SimReply) {
+            match self.recv_sim_reply() {
+                Ok(received_sim_reply) => assert_eq!(expected_reply, &received_sim_reply),
+                Err(e) => match e {
+                    ReceptionError::Io(ref io_error) => {
+                        if io_error.kind() == ErrorKind::WouldBlock {
+                            // Continue to perform regular checks like the stop signal.
+                            panic!("no simulation reply received");
+                        } else {
+                            // Handle unexpected errors (e.g., socket closed) here.
+                            panic!("unexpected request server error: {e}");
+                        }
+                    }
+                    ReceptionError::SerdeJson(json_error) => {
+                        panic!("unexpected JSON error: {json_error}");
+                    }
+                },
+            }
+        }
+    }
+    #[test]
+    fn test_basic_udp_request_reception() {
+        let (udp_testbench, mut udp_server) =
+            UdpTestbench::new(true, Some(SERVER_WAIT_TIME_MS), 10)
+                .expect("could not create testbench");
+        let server_thread = std::thread::spawn(move || udp_server.run());
+        let sim_request = SimRequest::new(PcduRequest::RequestSwitchInfo);
+        udp_testbench
+            .send_request(&sim_request)
+            .expect("sending request failed");
+        std::thread::sleep(Duration::from_millis(SERVER_WAIT_TIME_MS));
+        // Check that the sim request has arrives and was forwarded.
+        let received_sim_request = udp_testbench
+            .try_recv_request()
+            .expect("did not receive request");
+        assert_eq!(sim_request, received_sim_request);
+        // Stop the server.
+        udp_testbench.stop();
+        server_thread.join().unwrap();
+    }
+
+    #[test]
+    fn test_udp_reply_server() {
+        let (mut udp_testbench, mut udp_server) =
+            UdpTestbench::new(false, Some(SERVER_WAIT_TIME_MS), 10)
+                .expect("could not create testbench");
+        let server_thread = std::thread::spawn(move || udp_server.run());
+        udp_testbench
+            .send_request(&SimRequest::new(SimCtrlRequest::Ping))
+            .expect("sending request failed");
+
+        let sim_reply = SimReply::new(PcduReply::SwitchInfo(get_all_off_switch_map()));
+        udp_testbench.send_reply(&sim_reply);
+
+        udp_testbench.check_next_sim_reply(&sim_reply);
+
+        // Stop the server.
+        udp_testbench.stop();
+        server_thread.join().unwrap();
+    }
+
+    #[test]
+    fn test_udp_req_server_and_reply_sender() {
+        let (mut udp_testbench, mut udp_server) =
+            UdpTestbench::new(false, Some(SERVER_WAIT_TIME_MS), 10)
+                .expect("could not create testbench");
+
+        let server_thread = std::thread::spawn(move || udp_server.run());
+
+        // Send a ping so that the server knows the address of the client.
+        // Do not check that the request arrives on the receiver side, is done by other test.
+        udp_testbench
+            .send_request(&SimRequest::new(SimCtrlRequest::Ping))
+            .expect("sending request failed");
+
+        // Send a reply to the server, ensure it gets forwarded to the client.
+        let sim_reply = SimReply::new(PcduReply::SwitchInfo(get_all_off_switch_map()));
+        udp_testbench.send_reply(&sim_reply);
+        std::thread::sleep(Duration::from_millis(SERVER_WAIT_TIME_MS));
+
+        // Now we check that the reply server can send back replies to the client.
+        udp_testbench.check_next_sim_reply(&sim_reply);
+
+        udp_testbench.stop();
+        server_thread.join().unwrap();
+    }
+
+    #[test]
+    fn test_udp_replies_client_unconnected() {
+        let (mut udp_testbench, mut udp_server) =
+            UdpTestbench::new(true, None, 10).expect("could not create testbench");
+
+        let server_thread = std::thread::spawn(move || udp_server.run());
+
+        // Send a reply to the server. The client is not connected, so it won't get forwarded.
+        let sim_reply = SimReply::new(PcduReply::SwitchInfo(get_all_off_switch_map()));
+        udp_testbench.send_reply(&sim_reply);
+        std::thread::sleep(Duration::from_millis(10));
+
+        udp_testbench.check_no_sim_reply_available();
+
+        // Connect by sending a ping.
+        udp_testbench
+            .send_request(&SimRequest::new(SimCtrlRequest::Ping))
+            .expect("sending request failed");
+        std::thread::sleep(Duration::from_millis(SERVER_WAIT_TIME_MS));
+
+        udp_testbench.check_next_sim_reply(&sim_reply);
+
+        // Now we check that the reply server can sent back replies to the client.
+        udp_testbench.stop();
+        server_thread.join().unwrap();
+    }
+
+    #[test]
+    fn test_udp_reply_server_old_replies_overwritten() {
+        let (mut udp_testbench, mut udp_server) =
+            UdpTestbench::new(true, None, 3).expect("could not create testbench");
+
+        let server_thread = std::thread::spawn(move || udp_server.run());
+
+        // The server only caches up to 3 replies.
+        let sim_reply = SimReply::new(SimCtrlReply::Pong);
+        for _ in 0..4 {
+            udp_testbench.send_reply(&sim_reply);
+        }
+        std::thread::sleep(Duration::from_millis(20));
+
+        udp_testbench.check_no_sim_reply_available();
+
+        // Connect by sending a ping.
+        udp_testbench
+            .send_request(&SimRequest::new(SimCtrlRequest::Ping))
+            .expect("sending request failed");
+        std::thread::sleep(Duration::from_millis(SERVER_WAIT_TIME_MS));
+
+        for _ in 0..3 {
+            udp_testbench.check_next_sim_reply(&sim_reply);
+        }
+        udp_testbench.check_no_sim_reply_available();
+        udp_testbench.stop();
+        server_thread.join().unwrap();
+    }
+}

satrs/src/power.rs

@@ -24,6 +24,42 @@ pub enum SwitchState {
     Faulty = 3,
 }
 
+#[derive(Debug, Eq, PartialEq, Copy, Clone)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum SwitchStateBinary {
+    Off = 0,
+    On = 1,
+}
+
+impl TryFrom<SwitchState> for SwitchStateBinary {
+    type Error = ();
+    fn try_from(value: SwitchState) -> Result<Self, Self::Error> {
+        match value {
+            SwitchState::Off => Ok(SwitchStateBinary::Off),
+            SwitchState::On => Ok(SwitchStateBinary::On),
+            _ => Err(()),
+        }
+    }
+}
+
+impl<T: Into<u64>> From<T> for SwitchStateBinary {
+    fn from(value: T) -> Self {
+        if value.into() == 0 {
+            return SwitchStateBinary::Off;
+        }
+        SwitchStateBinary::On
+    }
+}
+
+impl From<SwitchStateBinary> for SwitchState {
+    fn from(value: SwitchStateBinary) -> Self {
+        match value {
+            SwitchStateBinary::Off => SwitchState::Off,
+            SwitchStateBinary::On => SwitchState::On,
+        }
+    }
+}
+
 pub type SwitchId = u16;
 
 /// Generic trait for a device capable of turning on and off switches.