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+# Internal & External Port Numbers
+
+- 80 and 443 are standard HTTP ports. Let them be.
+- Same for e-mail ports.
+- 8000-8999 are internal web application ports.
+  - Every app topic must use 80N0-80N9.
+- 9000 is the Prometheus port.
+  - Every exporter topic must use 90N0-90N9.
+  - For example, Node exporter can be on 9010.
+    Dovecot can be on 9020, Postfix can be on 9011,
+    and so on.
+- Haven't decided on redis, kresd etc. ports yet.