esdee

Esdee is a DNS-SD discovery client for Gleam on Erlang. It provides both selector-based and actor-based mechanisms to discover available service types and details.

The following example uses the discoverer actor to enumerate and print all service types and service details on you local network.

gleam add esdee@1

import esdee
import esdee/discoverer.{type Discoverer}
import gleam/erlang/process.{type Subject}
import gleam/io
import glip

type Discovered {
  ServiceType(String)
  ServiceDetails(esdee.ServiceDescription)
}

pub fn main() {
  // Create new discoverer that listens to both IPv4 and IPv6 DNS-SD messages
  let assert Ok(sd) =
    esdee.new()
    |> esdee.use_ipv6(True)
    |> discoverer.start()
  let sd = sd.data

  // Set up subjects for both service type and details discovery results
  let types = process.new_subject()
  let details = process.new_subject()

  // Subscribe to available service types,
  // and send a query for all available service types.
  discoverer.subscribe_to_service_types(sd, types)
  let assert Ok(_) = discoverer.poll_service_types(sd)

  // Combine both types of updates into one selector for printing
  let selector =
    process.new_selector()
    |> process.select_map(types, ServiceType)
    |> process.select_map(details, ServiceDetails)

  // Start handling updates
  recieve_forever(sd, selector, details)
}

fn recieve_forever(
  discoverer: Discoverer,
  selector: process.Selector(Discovered),
  details: Subject(esdee.ServiceDescription),
) -> Nil {
  let discovered = process.selector_receive_forever(selector)

  case discovered {
    ServiceType(service_type) -> {
      io.println("Discovered service type: " <> service_type)

      // When a service type is discovered,
      // subscribe to the details of and send a query for that type.
      // No duplicate subscriptions will be created,
      // but duplicate detail queries might be sent,
      // as we aren't doing any filtering on the types.
      discoverer.subscribe_to_service_details(discoverer, service_type, details)
      let assert Ok(_) =
        discoverer.poll_service_details(discoverer, service_type)
      Nil
    }

    ServiceDetails(description) -> {
      io.println(
        description.service_type
        <> " -> "
        <> description.target_name
        <> " @ "
        <> glip.ip_to_string(description.ip),
      )
    }
  }

  recieve_forever(discoverer, selector, details)
}

Common tasks:

gleam run   # Run the project
gleam test  # Run the tests
gleam dev   # Discover all your local services