@collight/dns-sd/dist/cjs/browser/Browser.cjs.map

A DNS Service Discovery implementation in modern TypeScript

{"version":3,"file":"Browser.cjs","sources":["../../../src/browser/Browser.ts"],"sourcesContent":["import { RemoteInfo } from 'dgram';\nimport { EventEmitter } from 'events';\nimport { MulticastDNS, ResponsePacket } from 'multicast-dns';\n\nimport { debug, nameEquals, ServiceType } from '../utils';\nimport { DiscoveredService } from './DiscoveredService';\n\n// MARK: BrowserFilter\nexport type BrowserFilter = {\n  /**\n   * Network protocol used by the service, either TCP or UDP.\n   * @default 'tcp'\n   */\n  protocol: 'tcp' | 'udp';\n  /**\n   * The service type to browse for. This corresponds to the DNS-SD service type without the leading underscore.\n   * @example 'http', 'ipp'\n   */\n  type: string;\n  /**\n   * Optional service subtypes to filter for. When provided, the browser targets this instance specifically.\n   * @example ['foo', 'bar']\n   */\n  subtypes?: string[];\n\n  /**\n   * Optional specific instance name to filter for. When provided, the browser targets this instance specifically.\n   * @example 'MyPrinter'\n   */\n  name?: string | RegExp;\n  /**\n   * Optional TXT record key-value pairs to filter discovered services.\n   * Only services whose TXT records match all keys and values will be emitted.\n   */\n  txt?: Record<string, string | RegExp>;\n};\n\n// MARK: BrowserOptions\nexport interface BrowserOptions {\n  filter?: BrowserFilter;\n}\n\ninterface BrowserEventMap {\n  up: [service: DiscoveredService];\n  down: [service: DiscoveredService];\n  update: [curr: DiscoveredService, prev: DiscoveredService];\n}\n\n// MARK: Browser\n/**\n * Browses the local network for mDNS/DNS-SD service instances.\n *\n * Emits:\n * - `up`: when a new service appears.\n * - `down`: when a previously seen service sends a \"goodbye\" (TTL = 0).\n * - `update`: when an existing service has received new records\n */\nexport class Browser extends EventEmitter<BrowserEventMap> {\n  static TLD = '.local';\n  static WILDCARD = '_services._dns-sd._udp' + this.TLD;\n\n  services: DiscoveredService[] = [];\n\n  private mdns: MulticastDNS;\n  private filter?: BrowserFilter;\n\n  private onresponse?: (packet: ResponsePacket, rinfo: RemoteInfo) => void;\n\n  constructor(mdns: MulticastDNS, options?: BrowserOptions) {\n    super();\n\n    this.mdns = mdns;\n    this.filter = options?.filter;\n  }\n\n  private get queryNames(): string[] {\n    if (!this.filter) {\n      return [Browser.WILDCARD];\n    }\n\n    const { protocol, type, name, subtypes } = this.filter;\n    const types =\n      subtypes && subtypes.length > 0\n        ? subtypes.map(subtype => new ServiceType(type, protocol, subtype).toString())\n        : [new ServiceType(type, protocol).toString()];\n\n    return types.map((typeStr: string) =>\n      typeof name === 'string' ? `${name}.${typeStr}${Browser.TLD}` : `${typeStr}${Browser.TLD}`,\n    );\n  }\n\n  /**\n   * Starts the browser and begins listening for mDNS service announcements.\n   * - Has no effect if the browser is already started.\n   */\n  start(): void {\n    if (this.onresponse) return;\n\n    this.onresponse = (packet: ResponsePacket, rinfo: RemoteInfo): void => {\n      debug('mdns on response packet:', packet);\n\n      // Handle goodbye records (TTL = 0) to remove offline services\n      // See https://tools.ietf.org/html/rfc6762#section-8.4\n      for (const answer of [...packet.answers, ...packet.additionals]) {\n        if (answer.type === 'PTR' && answer.ttl === 0) {\n          this.removeService(answer.data);\n        }\n      }\n\n      // Discover new services from valid responses\n      const services = DiscoveredService.fromResponse(packet, rinfo);\n      if (services.length === 0) {\n        if (!this.filter) {\n          // Initial wildcard query will only give PTR, need to query each one manually\n          for (const answer of packet.answers) {\n            if (answer.type !== 'PTR' || answer.name !== Browser.WILDCARD) continue;\n            debug('mdns wildcard query with:', answer.data);\n            this.mdns.query(answer.data, 'PTR');\n          }\n        }\n        return;\n      }\n\n      for (const service of services) {\n        if (this.services.some(s => nameEquals(s.fqdn, service.fqdn))) {\n          this.updateService(service);\n        } else {\n          this.addService(service);\n        }\n      }\n    };\n\n    this.mdns.on('response', this.onresponse);\n\n    // trigger initial query\n    this.update();\n  }\n\n  /**\n   * Stops the browser from listening to mDNS service announcements.\n   * - Has no effect if the browser is already stopped\n   */\n  stop(): void {\n    if (!this.onresponse) return;\n\n    this.mdns.removeListener('response', this.onresponse);\n    this.onresponse = undefined;\n\n    for (const service of this.services) {\n      clearTimeout(service.ttlTimer);\n    }\n    this.services = [];\n  }\n\n  /**\n   * Sends an active query to refresh the list of discovered services.\n   * - Triggers a new PTR record query for the configured service name\n   * - Causes mDNS responders to reply with their current service information\n   * - Useful for manual refresh when you suspect stale service data\n   */\n  update(): void {\n    // Actively query for service PTR records\n    debug('mdns query with:', this.queryNames);\n    for (const queryName of this.queryNames) {\n      this.mdns.query(queryName, 'PTR');\n    }\n  }\n\n  // MARK: private\n  private match(service: DiscoveredService): boolean {\n    if (!this.filter) {\n      return true;\n    }\n    const { protocol, type, subtypes, name, txt } = this.filter;\n    if (protocol !== service.protocol) {\n      return false;\n    }\n    if (type !== service.type) {\n      return false;\n    }\n    if (subtypes?.some(s => !service.subtypes.includes(s)) ?? false) {\n      return false;\n    }\n    if (name !== undefined) {\n      if (typeof name === 'string' && !nameEquals(name, service.name)) {\n        return false;\n      }\n      if (name instanceof RegExp && !name.test(service.name)) {\n        return false;\n      }\n    }\n    if (txt) {\n      for (const [key, value] of Object.entries(txt)) {\n        if (service.txt?.[key] === undefined) {\n          return false;\n        }\n        if (typeof value === 'string' && value !== service.txt[key]) {\n          return false;\n        }\n        if (value instanceof RegExp && !value.test(service.txt[key])) {\n          return false;\n        }\n      }\n    }\n    return true;\n  }\n\n  /**\n   * TODO: {@link https://datatracker.ietf.org/doc/html/rfc6762#section-5.2 | Continuous Multicast DNS Querying}\n   */\n  private setupTTLTimer(service: DiscoveredService): void {\n    if (service.ttl !== undefined) {\n      service.ttlTimer = setTimeout(() => {\n        if (service.expired) {\n          this.removeService(service.fqdn);\n        }\n      }, service.ttl * 1000);\n    }\n  }\n\n  private addService(service: DiscoveredService): void {\n    if (!this.match(service)) {\n      return;\n    }\n\n    this.services.push(service);\n\n    this.setupTTLTimer(service);\n\n    this.emit('up', service);\n  }\n\n  private updateService(service: DiscoveredService): void {\n    // If the new updated service no longer matches the filter, remove the service\n    if (!this.match(service)) {\n      this.removeService(service.fqdn);\n      return;\n    }\n\n    // Replace the old service instance\n    for (let i = 0; i < this.services.length; ++i) {\n      const s = this.services[i]!;\n      if (nameEquals(s.fqdn, service.fqdn)) {\n        clearTimeout(s.ttlTimer);\n        this.services[i] = service;\n\n        this.setupTTLTimer(service);\n\n        this.emit('update', service, s);\n        break;\n      }\n    }\n  }\n\n  private removeService(fqdn: string): void {\n    for (let i = 0; i < this.services.length; ++i) {\n      const s = this.services[i];\n      if (s && nameEquals(s.fqdn, fqdn)) {\n        this.services.splice(i, 1);\n        clearTimeout(s.ttlTimer);\n        this.emit('down', s);\n        return;\n      }\n    }\n  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