diff --git a/src/matrix/Reconnecter.js b/src/matrix/Reconnecter.js
new file mode 100644
index 00000000..ccff2203
--- /dev/null
+++ b/src/matrix/Reconnecter.js
@@ -0,0 +1,164 @@
+class Clock {
+    // use cases
+    // StopWatch: not sure I like that name ... but measure time difference from start to current time
+    // Timeout: wait for a given number of ms, and be able to interrupt the wait
+    //  Clock.timeout() -> creates a new timeout?
+    // Now: get current timestamp
+    //  Clock.now(), or pass Clock.now so others can do now()
+    // 
+    // should use subinterfaces so we can only pass part needed to other constructors
+    // 
+}
+
+
+// need to prevent memory leaks here!
+export class DomOnlineDetected {
+    constructor(reconnecter) {
+        // window.addEventListener('offline', () => appendOnlineStatus(false));
+        // window.addEventListener('online', () => appendOnlineStatus(true));
+        // appendOnlineStatus(navigator.onLine);
+        // on online, reconnecter.tryNow()
+    }
+}
+
+export class ExponentialRetryDelay {
+    constructor(start = 2000, delay) {
+        this._start = start;
+        this._current = start;
+        this._delay = delay;
+        this._max = 60 * 5 * 1000; //5 min
+        this._timer = null;
+    }
+
+    async waitForRetry() {
+        this._timer = this._delay(this._current);
+        try {
+            await this._timer.timeout();
+            // only increase delay if we didn't get interrupted
+            const seconds = this._current / 1000;
+            const powerOfTwo = (seconds * seconds) * 1000;
+            this._current = Math.max(this._max, powerOfTwo);
+        } finally {
+            this._timer = null;
+        }
+    }
+
+    reset() {
+        this._current = this._start;
+        if (this._timer) {
+            this._timer.abort();
+        }
+    }
+
+    get nextValue() {
+        return this._current;
+    }
+}
+
+// we need a clock interface that gives us both timestamps and a timer that we can interrupt?
+
+// state
+// - offline
+// - waiting to reconnect
+// - reconnecting
+// - online
+// 
+// 
+
+function createEnum(...values) {
+    const obj = {};
+    for (const value of values) {
+        obj[value] = value;
+    }
+    return Object.freeze(obj);
+}
+
+export const ConnectionState = createEnum(
+    "Offline",
+    "Waiting",
+    "Reconnecting",
+    "Online"
+);
+
+export class Reconnecter {
+    constructor({hsApi, retryDelay, clock}) {
+        this._online 
+        this._retryDelay = retryDelay;
+        this._currentDelay = null;
+        this._hsApi = hsApi;
+        this._clock = clock;
+        // assume online, and do our thing when something fails
+        this._state = ConnectionState.Online;
+        this._isReconnecting = false;
+        this._versionsResponse = null;
+    }
+
+    get lastVersionsResponse() {
+        return this._versionsResponse;
+    }
+
+    get state() {
+        return this._state;
+    }
+
+    get retryIn() {
+        return  this._stateSince.measure();
+    }
+
+    onRequestFailed() {
+        if (!this._isReconnecting) {
+            this._setState(ConnectionState.Offline);
+            // do something with versions response of loop here?
+            // we might want to pass it to session to know what server supports?
+            // so emit it ...
+            this._reconnectLoop();
+            // start loop
+        }
+    }
+
+    // don't throw from here
+    tryNow() {
+        // skip waiting
+        if (this._currentDelay) {
+            this._currentDelay.abort();
+        }
+    }
+
+    _setState(state) {
+        if (state !== this._state) {
+            this._state = state;
+            if (this._state === ConnectionState.Waiting) {
+                this._stateSince = this._clock.stopwatch();
+            } else {
+                this._stateSince = null;
+            }
+            this.emit("change", state);
+        }
+    }
+    
+    async _reconnectLoop() {
+        this._isReconnecting = true;
+        this._retryDelay.reset();
+        this._versionsResponse = null;
+
+        while (!this._versionsResponse) {
+            try {
+                this._setState(ConnectionState.Reconnecting);
+                const versionsRequest = this._hsApi.versions(10000);
+                this._versionsResponse = await versionsRequest.response();
+                this._setState(ConnectionState.Online);
+            } catch (err) {
+                this._setState(ConnectionState.Waiting);
+                this._currentDelay = this._retryDelay.next();
+                try {
+                    await this._currentDelay
+                } catch (err) {
+                    // waiting interrupted, we should retry immediately,
+                    // swallow error
+                } finally {
+                    this._currentDelay = null;
+                }
+            }
+        }
+    }
+}
diff --git a/src/matrix/hs-api.js b/src/matrix/hs-api.js
index ec8adad0..4a2747d7 100644
--- a/src/matrix/hs-api.js
+++ b/src/matrix/hs-api.js
@@ -40,7 +40,7 @@ export default class HomeServerApi {
         return `${this._homeserver}/_matrix/client/r0${csPath}`;
     }
 
-    _request(method, csPath, queryParams = {}, body) {
+    _request(method, url, queryParams = {}, body) {
         const queryString = Object.entries(queryParams)
             .filter(([, value]) => value !== undefined)
             .map(([name, value]) => {
@@ -50,7 +50,7 @@ export default class HomeServerApi {
                 return `${encodeURIComponent(name)}=${encodeURIComponent(value)}`;
             })
             .join("&");
-        const url = this._url(`${csPath}?${queryString}`);
+        url = `${url}?${queryString}`;
         let bodyString;
         const headers = new Headers();
         if (this._accessToken) {
@@ -70,15 +70,15 @@ export default class HomeServerApi {
     }
 
     _post(csPath, queryParams, body) {
-        return this._request("POST", csPath, queryParams, body);
+        return this._request("POST", this._url(csPath), queryParams, body);
     }
 
     _put(csPath, queryParams, body) {
-        return this._request("PUT", csPath, queryParams, body);
+        return this._request("PUT", this._url(csPath), queryParams, body);
     }
 
     _get(csPath, queryParams, body) {
-        return this._request("GET", csPath, queryParams, body);
+        return this._request("GET", this._url(csPath), queryParams, body);
     }
 
     sync(since, filter, timeout) {
@@ -108,4 +108,9 @@ export default class HomeServerApi {
     createFilter(userId, filter) {
         return this._post(`/user/${encodeURIComponent(userId)}/filter`, undefined, filter);
     }
+
+    versions(timeout) {
+        // TODO: implement timeout
+        return this._request("GET", `${this._homeserver}/_matrix/client/versions`);
+    }
 }