fabric
Ports
The concept of a port in Microbus can mean one of two things: a real TCP port, or a virtual emulated port.
Real TCP Ports
Microbus uses actual TCP ports for a few use cases.
The [HTTP ingress proxy](/docs/structure/coreservices-httpingress.html) listens for incoming HTTP requests on one or more TCP ports, by default `:8080`. A public-facing HTTP ingress proxy in a production setting will most likely be configured to listen on the standard HTTP ports `:443` and `:80`. Similarly, the [SMTP ingress proxy](/docs/structure/coreservices-smtpingress.html) listens on port `:25` for incoming SMTP messages. All microservices connect to the NATS messaging bus, by default on port `:4222`. Microservice exchange messages with other microservice over this bi-directional multiplexed connection. Telemetry is pushed to via OpenTelemetry on ports `:4317` (gRPC) or `:4318` (HTTP) to [Grafana](https://grafana.com/). The UI of Grafana is exposed on port `:3000` by default. ### Emulated Ports Microservices communicate with each other using an [emulation of the HTTP protocol](/docs/blocks/unicast.html) that includes the concept of ports. Real TCP ports are not opened. Rather, the virtual port number is made [part of the bus subject](/docs/blocks/unicast.html#notes-on-subscription-subjects) on which microservices listen for messages. By convention, some of these internal ports have a special purpose. Port `:888` is reserved for the [control plane](/docs/tech/control-subs.html). Endpoints defined on port `:443` or `:80` are typically considered public and exposed by the [HTTP ingress proxy](/docs/structure/coreservices-httpingress.html) to external users. Port `:444` is used by convention for endpoints that should remain internal. Any port not exposed by the ingress proxy would serve the same purpose. Port `:417` is the default port used for [events](/docs/blocks/events.html). An endpoint that subscribes on port `:0` receives messages on any port.