diff --git a/central_backend/src/constants.rs b/central_backend/src/constants.rs
index 4bd652d..5c44b09 100644
--- a/central_backend/src/constants.rs
+++ b/central_backend/src/constants.rs
@@ -6,6 +6,9 @@ pub const SESSION_COOKIE_NAME: &str = "X-session-cookie";
 /// Energy refresh operations interval
 pub const ENERGY_REFRESH_INTERVAL: Duration = Duration::from_secs(30);
 
+/// Maximum time after a ping during which a device is considered "up"
+pub const DEVICE_MAX_PING_TIME: u64 = 30;
+
 /// Fallback value to use if production cannot be fetched
 pub const FALLBACK_PRODUCTION_VALUE: i32 = 5000;
 
diff --git a/central_backend/src/energy/energy_actor.rs b/central_backend/src/energy/energy_actor.rs
index 982cccf..7528601 100644
--- a/central_backend/src/energy/energy_actor.rs
+++ b/central_backend/src/energy/energy_actor.rs
@@ -5,12 +5,33 @@ use crate::devices::device::{
 use crate::devices::devices_list::DevicesList;
 use crate::energy::consumption;
 use crate::energy::consumption::EnergyConsumption;
+use crate::utils::time_utils::time_secs;
 use actix::prelude::*;
 use openssl::x509::X509Req;
+use std::collections::HashMap;
+
+#[derive(Default)]
+struct DeviceState {
+    last_ping: u64,
+}
+
+impl DeviceState {
+    fn is_online(&self) -> bool {
+        (time_secs() - self.last_ping) < constants::DEVICE_MAX_PING_TIME
+    }
+}
+
+#[derive(Default)]
+struct RelayState {
+    enabled: bool,
+    since: usize,
+}
 
 pub struct EnergyActor {
     curr_consumption: EnergyConsumption,
     devices: DevicesList,
+    devices_state: HashMap<DeviceId, DeviceState>,
+    relays_state: HashMap<DeviceRelayID, RelayState>,
 }
 
 impl EnergyActor {
@@ -18,9 +39,20 @@ impl EnergyActor {
         Ok(Self {
             curr_consumption: consumption::get_curr_consumption().await?,
             devices: DevicesList::load()?,
+            devices_state: Default::default(),
+            relays_state: Default::default(),
         })
     }
 
+    fn device_state(&mut self, dev_id: &DeviceId) -> &mut DeviceState {
+        if !self.devices_state.contains_key(dev_id) {
+            self.devices_state
+                .insert(dev_id.clone(), Default::default());
+        }
+
+        self.devices_state.get_mut(dev_id).unwrap()
+    }
+
     async fn refresh(&mut self) -> anyhow::Result<()> {
         // Refresh energy
         self.curr_consumption = consumption::get_curr_consumption()
@@ -253,6 +285,9 @@ impl Handler<SynchronizeDevice> for EnergyActor {
     type Result = anyhow::Result<Vec<RelaySyncStatus>>;
 
     fn handle(&mut self, msg: SynchronizeDevice, _ctx: &mut Context<Self>) -> Self::Result {
+        let s = self.device_state(&msg.0);
+        s.last_ping = time_secs();
+
         // TODO : implement real code
         let mut v = vec![];
         for i in 0..msg.1.max_relays {
@@ -263,3 +298,34 @@ impl Handler<SynchronizeDevice> for EnergyActor {
         Ok(v)
     }
 }
+
+#[derive(serde::Serialize)]
+pub struct ResDevState {
+    id: DeviceId,
+    last_ping: u64,
+    online: bool,
+}
+
+/// Get the state of devices
+#[derive(Message)]
+#[rtype(result = "Vec<ResDevState>")]
+pub struct GetDevicesState;
+
+impl Handler<GetDevicesState> for EnergyActor {
+    type Result = Vec<ResDevState>;
+
+    fn handle(&mut self, _msg: GetDevicesState, _ctx: &mut Context<Self>) -> Self::Result {
+        self.devices
+            .full_list()
+            .into_iter()
+            .map(|d| {
+                let s = self.device_state(&d.id);
+                ResDevState {
+                    id: d.id,
+                    last_ping: time_secs() - s.last_ping,
+                    online: s.is_online(),
+                }
+            })
+            .collect()
+    }
+}
diff --git a/central_backend/src/server/servers.rs b/central_backend/src/server/servers.rs
index fd3f7c8..1dd4b4d 100644
--- a/central_backend/src/server/servers.rs
+++ b/central_backend/src/server/servers.rs
@@ -144,6 +144,10 @@ pub async fn secure_server(energy_actor: EnergyActorAddr) -> anyhow::Result<()>
                 "/web_api/devices/list_validated",
                 web::get().to(devices_controller::list_validated),
             )
+            .route(
+                "/web_api/devices/state",
+                web::get().to(devices_controller::devices_state),
+            )
             .route(
                 "/web_api/device/{id}",
                 web::get().to(devices_controller::get_single),
diff --git a/central_backend/src/server/web_api/devices_controller.rs b/central_backend/src/server/web_api/devices_controller.rs
index fd65701..cb657c5 100644
--- a/central_backend/src/server/web_api/devices_controller.rs
+++ b/central_backend/src/server/web_api/devices_controller.rs
@@ -28,6 +28,13 @@ pub async fn list_validated(actor: WebEnergyActor) -> HttpResult {
     Ok(HttpResponse::Ok().json(list))
 }
 
+/// Get the state of devices
+pub async fn devices_state(actor: WebEnergyActor) -> HttpResult {
+    let states = actor.send(energy_actor::GetDevicesState).await?;
+
+    Ok(HttpResponse::Ok().json(states))
+}
+
 #[derive(serde::Deserialize)]
 pub struct DeviceInPath {
     id: DeviceId,