Optionaloptions: ServerEngineOptionsOptionalclientStatic Readonlyregistrythe cumulated number of sessions that have been opened since this object exists
the cumulated number of subscriptions that have been created since this object exists
the number of active sessions
the number of active subscriptions.
the namespace of the Sessions and of the diagnostics of the Subscriptions (see diagnosticsNamespaceUri)
where the nodes to monitor are found: the node objects, and the compact address space for the namespaces it serves
the name of the server
the urn of the server namespace
the server urn
id: the id the subscription keeps, when it comes from another thread of the server
Optionalid: numberProtected_Optional[captureThe Symbol.for('nodejs.rejection') method is called in case a
promise rejection happens when emitting an event and
captureRejections is enabled on the emitter.
It is possible to use events.captureRejectionSymbol in
place of Symbol.for('nodejs.rejection').
import { EventEmitter, captureRejectionSymbol } from 'node:events';
class MyClass extends EventEmitter {
constructor() {
super({ captureRejections: true });
}
[captureRejectionSymbol](err, event, ...args) {
console.log('rejection happened for', event, 'with', err, ...args);
this.destroy(err);
}
destroy(err) {
// Tear the resource down here.
}
}
whether one more Session fits (OPC 10000-4 5.6.2): when the server is full, the oldest Session not activated yet is closed to make room, and a Session is refused only if none is
{Boolean} : true if session's subscription shall be deleted
Optionalreason: ClosingReason
the reason for closing the session ( shall be "Timeout", "Terminated" or "CloseSession")
OptionalauditEntryId: string
the RequestHeader.auditEntryId of the CloseSession request that caused this close, when there is one. See ServerSession#close.
If a Client invokes the CloseSession Service then all Subscriptions associated with the Session are also deleted if the deleteSubscriptions flag is set to TRUE. If a Server terminates a Session for any other reason, Subscriptions associated with the Session, are not deleted. Each Subscription has its own lifetime to protect against data loss in the case of a Session termination. In these cases, the Subscription can be reassigned to another Client before its lifetime expires.
create a new server session object.
Optionaloptions: CreateSessionOptionSynchronously 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
Returns an array listing the events for which the emitter has registered listeners.
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) ]
Read the current value of
ServerConfiguration.InApplicationSetup.
Returns false if the property does not exist in
the address space.
OptionalactiveOnly: booleanA snapshot of all sessions currently tracked by the engine (active and pending).
increment rejected session count (also increment rejected requests count)
increment rejected session count (also increment rejected requests count)
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.
The name of the event being listened for
Optionallistener: (...args: any[]) => void
The event handler function
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] ]
once the items of a CreateMonitoredItems (or a SetMonitoringMode, a ModifyMonitoredItems) are made: what they must wait for before the client hears of them. Nothing here, where items sample this engine's nodes directly (a session worker waits for its engine to watch them).
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
The name of the event.
The callback function
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
The name of the event.
The callback function
before the items of a CreateMonitoredItems are created: what must be fetched to find their nodes synchronously. Nothing here, where every node is (a session worker fetches them).
what a Read needs before its values are read: the asynchronous Variables refreshed (a front thread's engine fetches there what it cannot read in place, see RemoteEngine)
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.
The name of the event.
The callback function
Adds a one-time listener 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.
The name of the event.
The callback function
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');
read, without a promise: see AddressSpaceAccessor#readSync
OptionaldataValues: DataValue[]
an array containing value read The array length matches the number of nodeIds that are candidate for an async refresh (i.e: nodes that are of type Variable with asyncRefresh func }
Optionalcontext: ISessionContext
the session context of the read: given to the refresh function of each Variable
a namespace of the application served by the compact address space: registered on the node objects as well, so that the NamespaceArray and the indexes are one; nodes are then added through the compact space's own API (addVariable, addObject, bindings)
register a function that will be called when the server will perform its shut down.
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.
OptionaleventName: string | symbolRemoves 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 from
emit() 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 indexes 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.
the approximate number of seconds until the server will be shut down. The value is only relevant once the state changes into SHUTDOWN.
Set the ServerConfiguration.InApplicationSetup property
in the address space.
This flag indicates whether the server is currently in its initial application setup phase (e.g. waiting for GDS provisioning).
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.
Install a provider that contributes additional entries to the Server_ServerArray
variable (ns=0;i=2254).
OPC 10000-17 (GDS) Annex C.2 requires an aggregating server to expose the ServerUri
of every aggregated server in its ServerArray, so that ExpandedNodeId.serverIndex
values returned by services such as FindAlias can be resolved by clients.
The ServerArray value served to clients is [serverNameUrn, ...provider()]:
index 0 always remains this server's own URI, and the provider supplies the
entries for indices 1..n.
Index-stability contract: a serverIndex handed out to clients must keep
designating the same server for the lifetime of this server. The provider must
therefore never reorder or compact its array when a server is withdrawn; instead
it must leave an empty-string hole at the withdrawn position so that subsequent
indices do not shift.
The provider is consulted on every read of the variable, so its result should be
cheap to compute (e.g. a cached array). Pass null to remove a previously
installed provider. The provider may be installed before or after the server is
started.
{ServerSession} - the new session that will own the subscription
{IntegerId} - the subscription Id to transfer
{Boolean} - true if initial values will be resent.
Optionalcontext: ISessionContextOptionalcontext: ISessionContext
the compact address space, when the engine was initialized with one