an object that provides a certificate and a privateKey

Hierarchy (view full)

Constructors

Properties

Accessors

Methods

_apply_on_Subscription _apply_on_SubscriptionIds _apply_on_Subscriptions _beforeDeleteSubscription _on_AddNodes _on_AddReferences _on_BrowseNextRequest _on_CallRequest _on_Cancel _on_CreateMonitoredItemsRequest _on_CreateSessionRequest _on_CreateSubscriptionRequest _on_DeleteMonitoredItemsRequest _on_DeleteNodes _on_DeleteReferences _on_DeleteSubscriptionsRequest _on_HistoryReadRequest _on_HistoryUpdate _on_ModifyMonitoredItemsRequest _on_ModifySubscriptionRequest _on_PublishRequest _on_QueryFirst _on_QueryNext _on_ReadRequest _on_RegisterNodesRequest _on_RepublishRequest _on_SetMonitoringModeRequest _on_SetPublishingModeRequest _on_SetTriggeringRequest _on_TransferSubscriptionsRequest _on_TranslateBrowsePathsToNodeIdsRequest _on_UnregisterNodesRequest _on_WriteRequest [captureRejectionSymbol]? addListener createDefaultCertificate dispose emit eventNames getCertificate getCertificateChain getChannels getDiscoveryUrls getEndpointUrl getMaxListeners getPrivateKey getServers initialize initializeCM isUserAuthorized isValidUserIdentityToken isValidUserNameIdentityToken isValidX509IdentityToken listenerCount listeners makeServerNonce off once performPreInitialization prepare prependListener prependOnceListener raiseEvent rawListeners removeAllListeners removeListener resumeEndPoints setMaxListeners shutdown shutdownChannels start startAsync suspendEndPoints userNameIdentityTokenAuthenticateUser verifyClientSignature addAbortListener getEventListeners getMaxListeners listenerCount on once setMaxListeners

Events

Constructors

Properties

_preInitTask: any[]
allowAnonymous: boolean

false if anonymous connection are not allowed

capabilitiesForMDNS: string[]
certificateFile: string
discoveryServerEndpointUrl: string
endpoints: OPCUAServerEndPoint[]
engine: ServerEngine
maxConnectionsPerEndpoint: number

the maximum number for concurrent connection per end point

privateKeyFile: string
registerServerManager?: IRegisterServerManager
registerServerMethod: RegisterServerMethod
serverCertificateManager: OPCUACertificateManager
userCertificateManager: OPCUACertificateManager
userManager: UAUserManagerBase

the user manager

captureRejections: boolean

Value: boolean

Change the default captureRejections option on all new EventEmitter objects.

v13.4.0, v12.16.0

captureRejectionSymbol: typeof captureRejectionSymbol

Value: Symbol.for('nodejs.rejection')

See how to write a custom rejection handler.

v13.4.0, v12.16.0

defaultMaxListeners: number

By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListeners property can be used. If this value is not a positive number, a RangeError is thrown.

Take caution when setting the events.defaultMaxListeners because the change affects all EventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any single EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to temporarily avoid this warning:

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
// do stuff
emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

v0.11.2

defaultShutdownTimeout: number
deprecated_MAX_SUBSCRIPTION: number

the maximum number of subscription that can be created per server

errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an 'error' event is emitted. Therefore, the process will still crash if no regular 'error' listener is installed.

v13.6.0, v12.17.0

fallbackSessionName: string
makeServiceFault: ((statusCode: StatusCode, messages: string[]) => ServiceFault)

Type declaration

registry: ObjectRegistry
requestExactEndpointUrl: boolean

if requestExactEndpointUrl is set to true the server will only accept createSession that have a endpointUrl that strictly matches one of the provided endpoint. This mean that if the server expose a endpoint with url such as opc.tcp://MYHOSTNAME:1234, client will not be able to reach the server with the ip address of the server. requestExactEndpointUrl = true => emulates the Prosys Server behavior requestExactEndpointUrl = false => emulates the Unified Automation behavior.

Accessors

  • get buildInfo(): BuildInfo
  • The server build info

    Returns BuildInfo

  • get bytesRead(): number
  • total number of bytes read by the server since startup

    Returns number

  • get bytesWritten(): number
  • total number of bytes written by the server since startup

    Returns number

  • get currentChannelCount(): number
  • the number of connected channel on all existing end points

    Returns number

  • get currentSessionCount(): number
  • the number of sessions currently active

    Returns number

  • get currentSubscriptionCount(): number
  • The number of active subscriptions from all sessions

    Returns number

  • get initialized(): boolean
  • true if the server has been initialized

    Returns boolean

  • get isAuditing(): boolean
  • is the server auditing ?

    Returns boolean

  • get maxAllowedSessionNumber(): number
  • the maximum number of concurrent sessions allowed on the server

    Returns number

  • get publishingIntervalCount(): number
  • the publishing interval count

    Returns number

  • get rejectedRequestsCount(): number
  • the number of request that have been rejected

    Returns number

  • get rejectedSessionCount(): number
  • the number of session activation requests that have been rejected

    Returns number

  • get serverType(): ApplicationType
  • The type of server

    Returns ApplicationType

  • get sessionAbortCount(): number
  • the number of sessions that have been aborted

    Returns number

  • get transactionsCount(): number
  • Number of transactions processed by the server since startup

    Returns number

Methods

  • Parameters

    Returns Promise<void>

  • Parameters

    Returns Promise<void>

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns Promise<void>

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Type Parameters

    • K

    Parameters

    • error: Error
    • event: string | symbol
    • Rest...args: AnyRest

    Returns void

  • Alias for emitter.on(eventName, listener).

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v0.1.26

  • Returns Promise<void>

  • Returns void

  • Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

    Returns true if the event had listeners, false otherwise.

    import { EventEmitter } from 'node:events';
    const myEmitter = new EventEmitter();

    // First listener
    myEmitter.on('event', function firstListener() {
    console.log('Helloooo! first listener');
    });
    // Second listener
    myEmitter.on('event', function secondListener(arg1, arg2) {
    console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
    });
    // Third listener
    myEmitter.on('event', function thirdListener(...args) {
    const parameters = args.join(', ');
    console.log(`event with parameters ${parameters} in third listener`);
    });

    console.log(myEmitter.listeners('event'));

    myEmitter.emit('event', 1, 2, 3, 4, 5);

    // Prints:
    // [
    // [Function: firstListener],
    // [Function: secondListener],
    // [Function: thirdListener]
    // ]
    // Helloooo! first listener
    // event with parameters 1, 2 in second listener
    // event with parameters 1, 2, 3, 4, 5 in third listener

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol
    • Rest...args: AnyRest

    Returns boolean

    v0.1.26

  • Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

    import { EventEmitter } from 'node:events';

    const myEE = new EventEmitter();
    myEE.on('foo', () => {});
    myEE.on('bar', () => {});

    const sym = Symbol('symbol');
    myEE.on(sym, () => {});

    console.log(myEE.eventNames());
    // Prints: [ 'foo', 'bar', Symbol(symbol) ]

    Returns (string | symbol)[]

    v6.0.0

  • Returns Buffer

  • Returns Buffer

  • Returns string[]

  • get one of the possible endpointUrl

    Returns string

  • Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

    Returns number

    v1.0.0

  • Returns PrivateKey

  • Initialize the server by installing default node set.

    and instruct the server to listen to its endpoints.

    const server = new OPCUAServer();
    await server.initialize();

    // default server namespace is now initialized
    // it is a good time to create life instance objects
    const namespace = server.engine.addressSpace.getOwnNamespace();
    namespace.addObject({
    browseName: "SomeObject",
    organizedBy: server.engine.addressSpace.rootFolder.objects
    });

    // the addressSpace is now complete
    // let's now start listening to clients
    await server.start();

    Returns Promise<void>

  • Parameters

    • done: (() => void)
        • (): void
        • Returns void

    Returns void

  • Returns Promise<void>

  • Internal

    Parameters

    Returns void

  • Internal

    Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

      The name of the event being listened for

    • Optionallistener: Function

      The event handler function

    Returns number

    v3.2.0

  • Returns a copy of the array of listeners for the event named eventName.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });
    console.log(util.inspect(server.listeners('connection')));
    // Prints: [ [Function] ]

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

    Returns Function[]

    v0.1.26

  • Returns Buffer

  • Alias for emitter.removeListener().

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v10.0.0

  • Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

    server.once('connection', (stream) => {
    console.log('Ah, we have our first user!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.once('foo', () => console.log('a'));
    myEE.prependOnceListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v0.3.0

  • Returns Promise<void>

  • Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.prependListener('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v6.0.0

  • Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

    server.prependOnceListener('connection', (stream) => {
    console.log('Ah, we have our first user!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: ((...args: any[]) => void)

      The callback function

        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v6.0.0

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Internal

    Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Parameters

    Returns void

  • Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

    import { EventEmitter } from 'node:events';
    const emitter = new EventEmitter();
    emitter.once('log', () => console.log('log once'));

    // Returns a new Array with a function `onceWrapper` which has a property
    // `listener` which contains the original listener bound above
    const listeners = emitter.rawListeners('log');
    const logFnWrapper = listeners[0];

    // Logs "log once" to the console and does not unbind the `once` event
    logFnWrapper.listener();

    // Logs "log once" to the console and removes the listener
    logFnWrapper();

    emitter.on('log', () => console.log('log persistently'));
    // Will return a new Array with a single function bound by `.on()` above
    const newListeners = emitter.rawListeners('log');

    // Logs "log persistently" twice
    newListeners[0]();
    emitter.emit('log');

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol

    Returns Function[]

    v9.4.0

  • Removes all listeners, or those of the specified eventName.

    It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

    Returns a reference to the EventEmitter, so that calls can be chained.

    Parameters

    • OptionaleventName: string | symbol

    Returns this

    v0.1.26

  • Removes the specified listener from the listener array for the event named eventName.

    const callback = (stream) => {
    console.log('someone connected!');
    };
    server.on('connection', callback);
    // ...
    server.removeListener('connection', callback);

    removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

    Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

    import { EventEmitter } from 'node:events';
    class MyEmitter extends EventEmitter {}
    const myEmitter = new MyEmitter();

    const callbackA = () => {
    console.log('A');
    myEmitter.removeListener('event', callbackB);
    };

    const callbackB = () => {
    console.log('B');
    };

    myEmitter.on('event', callbackA);

    myEmitter.on('event', callbackB);

    // callbackA removes listener callbackB but it will still be called.
    // Internal listener array at time of emit [callbackA, callbackB]
    myEmitter.emit('event');
    // Prints:
    // A
    // B

    // callbackB is now removed.
    // Internal listener array [callbackA]
    myEmitter.emit('event');
    // Prints:
    // A

    Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

    When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

    import { EventEmitter } from 'node:events';
    const ee = new EventEmitter();

    function pong() {
    console.log('pong');
    }

    ee.on('ping', pong);
    ee.once('ping', pong);
    ee.removeListener('ping', pong);

    ee.emit('ping');
    ee.emit('ping');

    Returns a reference to the EventEmitter, so that calls can be chained.

    Type Parameters

    • K

    Parameters

    • eventName: string | symbol
    • listener: ((...args: any[]) => void)
        • (...args): void
        • Parameters

          • Rest...args: any[]

          Returns void

    Returns this

    v0.1.26

  • set all the end point into a state where they do accept connections note: this method is useful for testing purpose

    Returns Promise<void>

  • Parameters

    • callback: ((err?: Error) => void)
        • (err?): void
        • Parameters

          • Optionalerr: Error

          Returns void

    Returns void

  • By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

    Returns a reference to the EventEmitter, so that calls can be chained.

    Parameters

    • n: number

    Returns this

    v0.3.5

  • shutdown all server endpoints

    Parameters

    • Optionaltimeout: number

      the timeout (in ms) before the server is actually shutdown

    Returns Promise<void>

       // shutdown immediately
    server.shutdown(function(err) {
    });
      // in typescript with promises
    server.shutdown(10000).then(()=>{
    console.log("Server has shutdown");
    });
       // shutdown within 10 seconds
    server.engine.shutdownReason = coerceLocalizedText("Shutdown for maintenance");
    server.shutdown(10000,function(err) {
    });
  • shutdown all server endPoints

    Parameters

    • callback: ((err?: Error) => void)
        • (err?): void
        • Parameters

          • Optionalerr: Error

          Returns void

    Returns void

  • shutdown all server endPoints

    Parameters

    • timeout: number
    • callback: ((err?: Error) => void)
        • (err?): void
        • Parameters

          • Optionalerr: Error

          Returns void

    Returns void

  • Returns Promise<void>

  • Parameters

    • callback: ((err?: null | Error) => void)
        • (err?): void
        • Parameters

          • Optionalerr: null | Error

          Returns void

    Returns void

  • Initiate the server by starting all its endpoints

    Returns Promise<void>

  • start all registered endPoint, in parallel, and call done when all endPoints are listening.

    Parameters

    • done: (() => void)
        • (): void
        • Returns void

    Returns void

  • Returns Promise<void>

  • set all the end point into a state where they do not accept further connections

    note: this method is useful for testing purpose

    Returns Promise<void>

  • Parameters

    • callback: ((err?: Error) => void)
        • (err?): void
        • Parameters

          • Optionalerr: Error

          Returns void

    Returns void

  • Internal

    Parameters

    Returns void

  • Parameters

    Returns boolean

  • Experimental

    Listens once to the abort event on the provided signal.

    Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

    This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

    Returns a disposable so that it may be unsubscribed from more easily.

    import { addAbortListener } from 'node:events';

    function example(signal) {
    let disposable;
    try {
    signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
    disposable = addAbortListener(signal, (e) => {
    // Do something when signal is aborted.
    });
    } finally {
    disposable?.[Symbol.dispose]();
    }
    }

    Parameters

    • signal: AbortSignal
    • resource: ((event: Event) => void)
        • (event): void
        • Parameters

          • event: Event

          Returns void

    Returns Disposable

    Disposable that removes the abort listener.

    v20.5.0

  • Returns a copy of the array of listeners for the event named eventName.

    For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

    For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

    import { getEventListeners, EventEmitter } from 'node:events';

    {
    const ee = new EventEmitter();
    const listener = () => console.log('Events are fun');
    ee.on('foo', listener);
    console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
    }
    {
    const et = new EventTarget();
    const listener = () => console.log('Events are fun');
    et.addEventListener('foo', listener);
    console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
    }

    Parameters

    • emitter: EventTarget | EventEmitter<DefaultEventMap>
    • name: string | symbol

    Returns Function[]

    v15.2.0, v14.17.0

  • Returns the currently set max amount of listeners.

    For EventEmitters this behaves exactly the same as calling .getMaxListeners on the emitter.

    For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

    import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';

    {
    const ee = new EventEmitter();
    console.log(getMaxListeners(ee)); // 10
    setMaxListeners(11, ee);
    console.log(getMaxListeners(ee)); // 11
    }
    {
    const et = new EventTarget();
    console.log(getMaxListeners(et)); // 10
    setMaxListeners(11, et);
    console.log(getMaxListeners(et)); // 11
    }

    Parameters

    • emitter: EventTarget | EventEmitter<DefaultEventMap>

    Returns number

    v19.9.0

  • A class method that returns the number of listeners for the given eventName registered on the given emitter.

    import { EventEmitter, listenerCount } from 'node:events';

    const myEmitter = new EventEmitter();
    myEmitter.on('event', () => {});
    myEmitter.on('event', () => {});
    console.log(listenerCount(myEmitter, 'event'));
    // Prints: 2

    Parameters

    • emitter: EventEmitter<DefaultEventMap>

      The emitter to query

    • eventName: string | symbol

      The event name

    Returns number

    v0.9.12

    Since v3.2.0 - Use listenerCount instead.

  • import { on, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ee = new EventEmitter();

    // Emit later on
    process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
    });

    for await (const event of on(ee, 'foo')) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here

    Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

    An AbortSignal can be used to cancel waiting on events:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ac = new AbortController();

    (async () => {
    const ee = new EventEmitter();

    // Emit later on
    process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
    });

    for await (const event of on(ee, 'foo', { signal: ac.signal })) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here
    })();

    process.nextTick(() => ac.abort());

    Use the close option to specify an array of event names that will end the iteration:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ee = new EventEmitter();

    // Emit later on
    process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
    ee.emit('close');
    });

    for await (const event of on(ee, 'foo', { close: ['close'] })) {
    console.log(event); // prints ['bar'] [42]
    }
    // the loop will exit after 'close' is emitted
    console.log('done'); // prints 'done'

    Parameters

    • emitter: EventEmitter<DefaultEventMap>
    • eventName: string | symbol
    • Optionaloptions: StaticEventEmitterIteratorOptions

    Returns AsyncIterableIterator<any[]>

    An AsyncIterator that iterates eventName events emitted by the emitter

    v13.6.0, v12.16.0

  • Parameters

    • emitter: EventTarget
    • eventName: string
    • Optionaloptions: StaticEventEmitterIteratorOptions

    Returns AsyncIterableIterator<any[]>

  • Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

    This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

    import { once, EventEmitter } from 'node:events';
    import process from 'node:process';

    const ee = new EventEmitter();

    process.nextTick(() => {
    ee.emit('myevent', 42);
    });

    const [value] = await once(ee, 'myevent');
    console.log(value);

    const err = new Error('kaboom');
    process.nextTick(() => {
    ee.emit('error', err);
    });

    try {
    await once(ee, 'myevent');
    } catch (err) {
    console.error('error happened', err);
    }

    The special handling of the 'error' event is only used when events.once() is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

    import { EventEmitter, once } from 'node:events';

    const ee = new EventEmitter();

    once(ee, 'error')
    .then(([err]) => console.log('ok', err.message))
    .catch((err) => console.error('error', err.message));

    ee.emit('error', new Error('boom'));

    // Prints: ok boom

    An AbortSignal can be used to cancel waiting for the event:

    import { EventEmitter, once } from 'node:events';

    const ee = new EventEmitter();
    const ac = new AbortController();

    async function foo(emitter, event, signal) {
    try {
    await once(emitter, event, { signal });
    console.log('event emitted!');
    } catch (error) {
    if (error.name === 'AbortError') {
    console.error('Waiting for the event was canceled!');
    } else {
    console.error('There was an error', error.message);
    }
    }
    }

    foo(ee, 'foo', ac.signal);
    ac.abort(); // Abort waiting for the event
    ee.emit('foo'); // Prints: Waiting for the event was canceled!

    Parameters

    • emitter: EventEmitter<DefaultEventMap>
    • eventName: string | symbol
    • Optionaloptions: StaticEventEmitterOptions

    Returns Promise<any[]>

    v11.13.0, v10.16.0

  • Parameters

    • emitter: EventTarget
    • eventName: string
    • Optionaloptions: StaticEventEmitterOptions

    Returns Promise<any[]>

  • import { setMaxListeners, EventEmitter } from 'node:events';

    const target = new EventTarget();
    const emitter = new EventEmitter();

    setMaxListeners(5, target, emitter);

    Parameters

    • Optionaln: number

      A non-negative number. The maximum number of listeners per EventTarget event.

    • Rest...eventTargets: (EventTarget | EventEmitter<DefaultEventMap>)[]

    Returns void

    v15.4.0

Events

  • Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Parameters

    • event: "create_session"
    • eventHandler: ((session: ServerSession) => void)

    Returns this

    v0.1.101

  • Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Parameters

    • event: "session_activated"
    • eventHandler: ((session: ServerSession) => void)

    Returns this

    v0.1.101

  • Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Parameters

    • event: "session_closed"
    • eventHandler: ((session: ServerSession, reason: string) => void)
        • (session, reason): void
        • Parameters

          Returns void

    Returns this

    v0.1.101

  • Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Parameters

    • event: "post_initialize"
    • eventHandler: (() => void)
        • (): void
        • Returns void

    Returns this

    v0.1.101

  • emitted when the server is trying to registered the LDS but when the connection to the lds has failed serverRegistrationPending is sent when the backoff signal of the connection process is raised serverRegistrationPending

    Parameters

    • event: "serverRegistrationPending"
    • eventHandler: (() => void)
        • (): void
        • Returns void

    Returns this

  • event raised when server has been successfully registered on the local discovery server serverRegistered

    Parameters

    • event: "serverRegistered"
    • eventHandler: (() => void)
        • (): void
        • Returns void

    Returns this

  • event raised when server registration has been successfully renewed on the local discovery server serverRegistered

    Parameters

    • event: "serverRegistrationRenewed"
    • eventHandler: (() => void)
        • (): void
        • Returns void

    Returns this

  • event raised when server has been successfully unregistered from the local discovery server serverUnregistered

    Parameters

    • event: "serverUnregistered"
    • eventHandler: (() => void)
        • (): void
        • Returns void

    Returns this

  • event raised after the server has raised an OPCUA event toward a client

    Parameters

    • event: "event"
    • eventHandler: ((eventData: any) => void)
        • (eventData): void
        • Parameters

          • eventData: any

          Returns void

    Returns this

  • event raised when the server received a request from one of its connected client. useful for trace purpose.

    Parameters

    Returns this

  • event raised when the server send an response to a request to one of its connected client. useful for trace purpose.

    Parameters

    Returns this

  • event raised when a new secure channel is opened

    Parameters

    Returns this

  • event raised when a new secure channel is closed

    Parameters

    Returns this

  • event raised when the server refused a tcp connection from a client. ( for instance because too any connections)

    Parameters

    • event: "connectionRefused"
    • eventHandler: ((socketData: ISocketData, endpoint: OPCUAServerEndPoint) => void)
        • (socketData, endpoint): void
        • Parameters

          Returns void

    Returns this

  • event raised when a OpenSecureChannel has failed, it could be a invalid certificate or malformed message

    Parameters

    • event: "openSecureChannelFailure"
    • eventHandler: ((socketData: ISocketData, channelData: IChannelData, endpoint: OPCUAServerEndPoint) => void)
        • (socketData, channelData, endpoint): void
        • Parameters

          Returns void

    Returns this

  • Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

    server.on('connection', (stream) => {
    console.log('someone connected!');
    });

    Returns a reference to the EventEmitter, so that calls can be chained.

    By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

    import { EventEmitter } from 'node:events';
    const myEE = new EventEmitter();
    myEE.on('foo', () => console.log('a'));
    myEE.prependListener('foo', () => console.log('b'));
    myEE.emit('foo');
    // Prints:
    // b
    // a

    Parameters

    • event: string
    • eventHandler: ((...args: [any?, ...any[]]) => void)
        • (...args): void
        • Parameters

          • Rest...args: [any?, ...any[]]

          Returns void

    Returns this

    v0.1.101