added README

src/go/intercom/README.md

@@ -0,0 +1,43 @@
+# Intercom Module
+
+> TODO: improve upon this README
+
+The `intercom` module uses MQTT to extend an OT-sim device's message bus data
+to other OT-sim devices. This is helpful when, for example, multiple other
+OT-sim devices that are being used as HMI servers need to talk to the same
+remote OT-sim device. This could be done using DNP3, for example, but the DNP3
+module only supports a single client connection. Using the `intercom` module
+also cuts down on configuration requirements since it simply mirrors all tags
+automatically.
+
+## TODO
+
+* [ ] Update client and broker implementations to default to the following settings.
+
+```
+  <intercom mode="broker">
+    <endpoint>:1883</endpoint>
+    <publish>
+      <status>true</status>
+      <update>false</update>
+    </publish>
+    <subscribe>
+      <status>false</status>
+      <update>true</update>
+    </subscribe>
+  </intercom>
+```
+
+```
+  <intercom mode="client">
+    <endpoint>tcp://10.2.2.2:1883</endpoint>
+    <publish>
+      <status>false</status>
+      <update>true</update>
+    </publish>
+    <subscribe>
+      <status>true</status>
+      <update>false</update>
+    </subscribe>
+  </intercom>
+```