diff --git a/core/package.json b/core/package.json
index 0fea9f1..15f5f5e 100644
--- a/core/package.json
+++ b/core/package.json
@@ -15,6 +15,7 @@
     "test": "jest",
     "test-watch": "jest --watch",
     "prettify": "prettier --write .",
+    "tsc": "tsc",
     "compile": "rimraf dist && tsc"
   }
 }
diff --git a/core/src/TeaCup/ObjectSerializer.ts b/core/src/TeaCup/ObjectSerializer.ts
index dcd5dca..dda1973 100644
--- a/core/src/TeaCup/ObjectSerializer.ts
+++ b/core/src/TeaCup/ObjectSerializer.ts
@@ -1,3 +1,28 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 Rémi Van Keisbelck
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
 import { Dict } from './Dict';
 import { Tuple } from './Tuple';
 import { Just, Maybe, Nothing } from './Maybe';
diff --git a/core/src/TeaCup/Port.ts b/core/src/TeaCup/Port.ts
new file mode 100644
index 0000000..736e8e3
--- /dev/null
+++ b/core/src/TeaCup/Port.ts
@@ -0,0 +1,66 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 Rémi Van Keisbelck
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+import {Sub} from "./Sub";
+
+export class Port<T> {
+  private subs: PortSub<T, any>[] = [];
+
+  send(t: T): void {
+    this.subs.forEach((s) => s.notify(t));
+  }
+
+  subscribe<M>(f: (t: T) => M): Sub<M> {
+    return new PortSub(
+        f,
+        (p) => this.subs.push(p),
+        (p) => {
+          this.subs = this.subs.filter((x) => x !== p);
+        },
+    );
+  }
+}
+
+class PortSub<T, M> extends Sub<M> {
+  constructor(
+      private readonly f: (t: T) => M,
+      private readonly _onInit: (p: PortSub<T, M>) => void,
+      private readonly _onRelease: (p: PortSub<T, M>) => void,
+  ) {
+    super();
+  }
+
+  protected onInit() {
+    this._onInit(this);
+  }
+
+  protected onRelease() {
+    this._onRelease(this);
+  }
+
+  notify(t: T): void {
+    this.dispatch(this.f(t));
+  }
+}
diff --git a/core/src/TeaCup/index.ts b/core/src/TeaCup/index.ts
index 923a89c..81b77a4 100644
--- a/core/src/TeaCup/index.ts
+++ b/core/src/TeaCup/index.ts
@@ -42,3 +42,4 @@ export * from './ListWithSelection';
 export * from './ObjectSerializer';
 export * from './Try';
 export * from './UUID';
+export * from './Port';
diff --git a/samples/src/App.tsx b/samples/src/App.tsx
index d3f1a2f..d42dd20 100755
--- a/samples/src/App.tsx
+++ b/samples/src/App.tsx
@@ -55,6 +55,8 @@ import * as ClassMsgs from './Samples/ClassMsgs';
 import * as Sful from './Samples/StatefulInView';
 import * as Rest from './Samples/Rest';
 import * as TimeSample from './Samples/TimeSample';
+import * as PortsSample from './Samples/PortsSample';
+import {appSamplePorts} from "./Samples/PortsSample";
 
 enum Tab {
   All,
@@ -160,6 +162,7 @@ interface Samples {
   readonly sful: Sful.Model;
   readonly rest: Rest.Model;
   readonly time: TimeSample.Model;
+  readonly ports: PortsSample.Model;
 }
 
 type Msg =
@@ -172,6 +175,7 @@ type Msg =
   | { type: 'sful'; child: Sful.Msg }
   | { type: 'rest'; child: Rest.Msg }
   | { type: 'timeSample'; child: TimeSample.Msg }
+  | { type: 'portsSample'; child: PortsSample.Msg }
   | { type: 'urlChange'; location: Location }
   | { type: 'newUrl'; url: string }
   | { type: 'noop' }
@@ -189,6 +193,7 @@ function initSamples(): [Model, Cmd<Msg>] {
   const sful = Sful.init();
   const rest = Rest.init();
   const time = TimeSample.init();
+  const ports = PortsSample.init();
   return [
     {
       tag: 'samples',
@@ -202,6 +207,7 @@ function initSamples(): [Model, Cmd<Msg>] {
         sful: sful[0],
         rest: rest[0],
         time: time[0],
+        ports: ports[0],
       },
     },
     Cmd.batch([
@@ -214,6 +220,7 @@ function initSamples(): [Model, Cmd<Msg>] {
       sful[1].map(mapSful),
       rest[1].map(mapRest),
       time[1].map(mapTimeSample),
+      ports[1].map(mapPortsSample),
     ]),
   ];
 }
@@ -328,6 +335,13 @@ function mapTimeSample(m: TimeSample.Msg): Msg {
   };
 }
 
+function mapPortsSample(m: PortsSample.Msg): Msg {
+  return {
+    type: 'portsSample',
+    child: m,
+  }
+}
+
 function view(dispatch: Dispatcher<Msg>, model: Model) {
   switch (model.tag) {
     case 'home':
@@ -545,6 +559,12 @@ function viewSamples(dispatch: Dispatcher<Msg>, samples: Samples) {
       {Rest.view(map(dispatch, mapRest), samples.rest)}
       <h2>Time</h2>
       {TimeSample.view(map(dispatch, mapTimeSample), samples.time)}
+      <h2>Ports</h2>
+      {PortsSample.view(map(dispatch, mapPortsSample), samples.ports)}
+      <button onClick={() => {
+        // call ports without going through any update loop
+        appSamplePorts.setCounter.send(0)
+      }}>Reset using port</button>
     </div>
   );
 }
@@ -603,12 +623,16 @@ function update(msg: Msg, model: Model): [Model, Cmd<Msg>] {
         const macRest = Rest.update(msg.child, s.rest);
         return [{ ...s, rest: macRest[0] }, macRest[1].map(mapRest)];
       });
-
     case 'timeSample':
       return mapSample((s: Samples) => {
         const macTime = TimeSample.update(msg.child, s.time);
         return [{ ...s, time: macTime[0] }, macTime[1].map(mapTimeSample)];
       });
+    case "portsSample":
+      return mapSample((s: Samples) => {
+        const mac = PortsSample.update(msg.child, s.ports);
+        return [{ ...s, ports: mac[0]}, mac[1].map(mapPortsSample)];
+      });
 
     case 'urlChange':
       return init(msg.location);
@@ -631,6 +655,7 @@ function subscriptions(model: Model): Sub<Msg> {
         ParentChild.subscriptions(parentChild).map(mapParentChild),
         Raf.subscriptions(raf).map(mapRaf),
         TimeSample.subscriptions(time).map(mapTimeSample),
+        PortsSample.subscriptions().map(mapPortsSample),
       ]);
     default:
       return Sub.none();
diff --git a/samples/src/Samples/PortsSample.tsx b/samples/src/Samples/PortsSample.tsx
new file mode 100644
index 0000000..379ea0f
--- /dev/null
+++ b/samples/src/Samples/PortsSample.tsx
@@ -0,0 +1,77 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2019 Rémi Van Keisbelck
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+import * as React from 'react';
+import { Cmd, Dispatcher, noCmd, Port, Sub } from 'tea-cup-core';
+
+export type Model = number;
+
+export type Msg = { tag: 'inc' } | { tag: 'set-value'; value: number };
+
+function onSetValue(value: number): Msg {
+  return {
+    tag: 'set-value',
+    value,
+  };
+}
+
+// the ports allow to send Msgs to the update loop from the outside
+export const appSamplePorts = {
+  setCounter: new Port<number>(),
+};
+
+// export as a global to play in dev tools
+// @ts-ignore
+window['appSamplePorts'] = appSamplePorts;
+
+export function init(): [Model, Cmd<Msg>] {
+  return noCmd(0);
+}
+
+export function view(dispatch: Dispatcher<Msg>, model: Model) {
+  return (
+    <div>
+      <h2>Counter with ports</h2>
+      <span>Value = {model}</span>
+      <button onClick={() => dispatch({ tag: 'inc' })}>+</button>
+    </div>
+  );
+}
+
+export function update(msg: Msg, model: Model): [Model, Cmd<Msg>] {
+  switch (msg.tag) {
+    case 'inc': {
+      return noCmd(model + 1);
+    }
+    case 'set-value': {
+      return noCmd(msg.value);
+    }
+  }
+}
+
+export function subscriptions(): Sub<Msg> {
+  // wire ports to get Msgs into our update func
+  return appSamplePorts.setCounter.subscribe(onSetValue);
+}
diff --git a/tea-cup/package.json b/tea-cup/package.json
index f9a16de..713bc05 100644
--- a/tea-cup/package.json
+++ b/tea-cup/package.json
@@ -15,6 +15,7 @@
     "test": "jest",
     "test-watch": "jest --watch",
     "prettify": "prettier --write .",
+    "tsc": "tsc",
     "compile": "rimraf dist && tsc",
     "samples": "tsc --outFile ./dist/Samples/index.js && cp ./src/Samples/index.html ./dist/Samples"
   },
diff --git a/tea-cup/src/TeaCup/Program.ts b/tea-cup/src/TeaCup/Program.ts
index 946eeb0..da0fd4f 100644
--- a/tea-cup/src/TeaCup/Program.ts
+++ b/tea-cup/src/TeaCup/Program.ts
@@ -45,44 +45,24 @@ export interface ProgramProps<Model, Msg> {
 export class Program<Model, Msg> extends Component<ProgramProps<Model, Msg>, never> {
   readonly uuid = nextUuid();
   private readonly bd: Dispatcher<Msg>;
-  private readonly devTools?: DevTools<Model, Msg>;
   private count: number = 0;
-  private readonly initialCmd: Cmd<any>;
-  private currentModel: Model;
-  private currentSub: Sub<Msg>;
+  private initialCmd?: Cmd<any>;
+  private currentModel?: Model;
+  private currentSub?: Sub<Msg>;
 
   constructor(props: Readonly<ProgramProps<Model, Msg>>) {
     super(props);
-    this.devTools = this.props.devTools;
-    if (this.devTools) {
-      this.devTools.connected(this);
-    }
-    const mac = (this.devTools && this.devTools.initFromSnapshot()) || props.init();
-    if (this.devTools) {
-      this.fireEvent({
-        tag: 'init',
-        time: new Date().getTime(),
-        model: mac[0],
-      });
-    }
-    const sub = props.subscriptions(mac[0]);
-    this.currentModel = mac[0];
-    this.currentSub = sub;
-    // connect to sub
-    const d = this.dispatch.bind(this);
-    this.bd = d;
-    sub.init(d);
-    this.initialCmd = mac[1];
+    this.bd = this.dispatch.bind(this);
   }
 
   private fireEvent(e: DevToolsEvent<Model, Msg>) {
-    if (this.devTools) {
-      this.devTools.onEvent(e);
+    if (this.props.devTools) {
+      this.props.devTools.onEvent(e);
     }
   }
 
   dispatch(msg: Msg) {
-    if (this.devTools && this.devTools.isPaused()) {
+    if (this.props.devTools && this.props.devTools.isPaused()) {
       // do not process messages if we are paused
       return;
     }
@@ -90,62 +70,93 @@ export class Program<Model, Msg> extends Component<ProgramProps<Model, Msg>, nev
     this.count++;
     const count = this.count;
     const currentModel = this.currentModel;
-    const updated = this.props.update(msg, currentModel);
-    if (this.devTools) {
-      this.fireEvent({
-        tag: 'updated',
-        msgNum: count,
-        time: new Date().getTime(),
-        msg: msg,
-        modelBefore: currentModel,
-        modelAfter: updated[0],
-        cmd: updated[1],
-      });
-    }
-    const newSub = this.props.subscriptions(updated[0]);
-    const prevSub = this.currentSub;
+    if (currentModel) {
+      const updated = this.props.update(msg, currentModel);
+      if (this.props.devTools) {
+        this.fireEvent({
+          tag: 'updated',
+          msgNum: count,
+          time: new Date().getTime(),
+          msg: msg,
+          modelBefore: currentModel,
+          modelAfter: updated[0],
+          cmd: updated[1],
+        });
+      }
+      const newSub = this.props.subscriptions(updated[0]);
+      const prevSub = this.currentSub;
 
-    const d = this.dispatch.bind(this);
+      const d = this.dispatch.bind(this);
 
-    newSub.init(d);
-    prevSub.release();
+      newSub.init(d);
+      prevSub && prevSub.release();
 
-    // perform commands in a separate timout, to
-    // make sure that this dispatch is done
-    setTimeout(() => {
-      // console.log("dispatch: processing commands");
-      // debug("performing command", updated[1]);
-      updated[1].execute(d);
-      // debug("<<<  done");
-    }, 0);
+      // perform commands in a separate timout, to
+      // make sure that this dispatch is done
+      setTimeout(() => {
+        // console.log("dispatch: processing commands");
+        // debug("performing command", updated[1]);
+        updated[1].execute(d);
+        // debug("<<<  done");
+      }, 0);
 
-    this.currentModel = updated[0];
-    this.currentSub = newSub;
-    this.forceUpdate();
+      this.currentModel = updated[0];
+      this.currentSub = newSub;
+
+      // trigger rendering
+      this.forceUpdate();
+    }
   }
 
   componentDidMount() {
+    const { devTools } = this.props;
+    if (devTools) {
+      devTools.connected(this);
+    }
+    const mac = (devTools && devTools.initFromSnapshot()) || this.props.init();
+    if (devTools) {
+      this.fireEvent({
+        tag: 'init',
+        time: new Date().getTime(),
+        model: mac[0],
+      });
+    }
+    const sub = this.props.subscriptions(mac[0]);
+    this.currentModel = mac[0];
+    this.currentSub = sub;
+    // connect to sub
+    sub.init(this.bd);
+    this.initialCmd = mac[1];
+
     // trigger initial command
     setTimeout(() => {
-      this.initialCmd.execute(this.bd);
+      this.initialCmd && this.initialCmd.execute(this.bd);
     }, 0);
+
+    // trigger rendering after mount
+    this.forceUpdate();
   }
 
   render(): ReactNode {
-    return this.props.view(this.bd, this.currentModel);
+    if (this.currentModel && this.bd) {
+      return this.props.view(this.bd, this.currentModel);
+    }
+    return null;
   }
 
   setModel(model: Model, withSubs: boolean) {
-    let newSub: Sub<Msg>;
-    if (withSubs) {
-      newSub = this.props.subscriptions(model);
-    } else {
-      newSub = Sub.none();
+    if (this.bd) {
+      let newSub: Sub<Msg>;
+      if (withSubs) {
+        newSub = this.props.subscriptions(model);
+      } else {
+        newSub = Sub.none();
+      }
+      newSub.init(this.bd);
+      this.currentSub && this.currentSub.release();
+      this.currentModel = model;
+      this.currentSub = newSub;
+      this.forceUpdate();
     }
-    newSub.init(this.bd);
-    this.currentSub.release();
-    this.currentModel = model;
-    this.currentSub = newSub;
-    this.forceUpdate();
   }
 }