Abstract Class: BaseServer

Defined in: packages/microservices/src/transports/server.ts:20

Abstract base class for all built-in transport servers.

Maintains two separate handler registries:

• messageHandlers – request-response handlers (registered via MessagePattern).
• eventHandlers – fire-and-forget handlers (registered via EventPattern).

The unified addHandler method routes to messageHandlers for backward compatibility with code that does not distinguish between the two.

Extends

• EventEmitter

Extended by

• RabbitMQServer
• RedisServer
• TcpServer

Implements

• Server

Constructors

Constructor

new BaseServer(options?): BaseServer;

Defined in: node_modules/@types/node/events.d.ts:54

Parameters

Parameter	Type
options?	EventEmitterOptions

Returns

BaseServer

Inherited from

EventEmitter.constructor

Methods

[captureRejectionSymbol]()?

optional [captureRejectionSymbol](
   error, 
   event, 
   ...args
): void;

Defined in: node_modules/@types/node/events.d.ts:87

The 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.
  }
}

Parameters

Parameter	Type
error	Error
event	string | symbol
...args	any[]

Returns

void

Since

v13.4.0, v12.16.0

Inherited from

EventEmitter.[captureRejectionSymbol]

---

addEventHandler()

addEventHandler(pattern, callback): void;

Defined in: packages/microservices/src/transports/server.ts:50

Registers callback as a fire-and-forget event handler for pattern. The handler's return value is ignored.

Parameters

Parameter	Type
pattern	string
callback	MessageHandler

Returns

void

---

addHandler()

addHandler(pattern, callback): void;

Defined in: packages/microservices/src/transports/server.ts:33

Registers callback as a request-response handler for pattern. Equivalent to addMessageHandler.

Parameters

Parameter	Type
pattern	string
callback	MessageHandler

Returns

void

Implementation of

Server.addHandler

---

addListener()

addListener<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:92

Alias for emitter.on(eventName, listener).

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol
listener	(...args) => void

Returns

this

Since

v0.1.26

Inherited from

EventEmitter.addListener

---

addMessageHandler()

addMessageHandler(pattern, callback): void;

Defined in: packages/microservices/src/transports/server.ts:42

Registers callback as a request-response handler for pattern. The handler is expected to return a value that will be sent back to the caller.

Parameters

Parameter	Type
pattern	string
callback	MessageHandler

Returns

void

---

cleanup()

protected cleanup(): void;

Defined in: packages/microservices/src/transports/server.ts:89

Removes all EventEmitter listeners and clears both handler maps. Subclasses should call this in their close() implementation to prevent memory leaks.

Returns

void

---

close()

abstract close(): void;

Defined in: packages/microservices/src/transports/server.ts:61

Shut down the transport and release all resources.

Returns

void

Implementation of

Server.close

---

emit()

emit<E>(eventName, ...args): boolean;

Defined in: node_modules/@types/node/events.d.ts:134

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol
...args	any[]

Returns

boolean

Since

v0.1.26

Inherited from

EventEmitter.emit

---

emitError()

protected emitError(error): void;

Defined in: packages/microservices/src/transports/server.ts:76

Safely surfaces a transport-level error.

Node's EventEmitter throws ERR_UNHANDLED_ERROR when "error" is emitted with no registered listener, which would crash the whole process on a routine ECONNRESET, Redis blip, or malformed frame. This helper only re-emits when a listener is attached; otherwise it logs the error so it is never silently swallowed and never crashes the process.

Parameters

Parameter	Type
error	unknown

Returns

void

---

emitEvent()

abstract emitEvent<T>(pattern, data): void;

Defined in: packages/microservices/src/transports/server.ts:59

Publish a fire-and-forget event.

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
pattern	string
data	T

Returns

void

Implementation of

Server.emitEvent

---

eventNames()

eventNames(): (string | symbol)[];

Defined in: node_modules/@types/node/events.d.ts:154

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) ]

Returns

(string | symbol)[]

Since

v6.0.0

Inherited from

EventEmitter.eventNames

---

getMaxListeners()

getMaxListeners(): number;

Defined in: node_modules/@types/node/events.d.ts:161

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

Returns

number

Since

v1.0.0

Inherited from

EventEmitter.getMaxListeners

---

handleEvent()

protected handleEvent<T>(
   pattern, 
   data, 
   ctx
): unknown;

Defined in: packages/microservices/src/transports/server.ts:116

Dispatches an incoming event to the matching event handler and returns the handler's result so transports can await it before acknowledging the message. Silently ignores events without a registered handler.

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
pattern	string
data	T
ctx	Record<string, unknown>

Returns

unknown

---

handleMessage()

protected handleMessage<T, R>(
   pattern, 
   data, 
   ctx
): unknown;

Defined in: packages/microservices/src/transports/server.ts:99

Dispatches an incoming request to the matching message handler.

Type Parameters

Type Parameter	Default type
T	unknown
R	unknown

Parameters

Parameter	Type
pattern	string
data	T
ctx	Record<string, unknown>

Returns

unknown

Throws

When no handler is registered for pattern.

---

listen()

abstract listen(callback?): void | Promise<void>;

Defined in: packages/microservices/src/transports/server.ts:63

Start the transport server.

Parameters

Parameter	Type	Description
callback?	(err?) => void	Called when the server is ready or has failed.

Returns

void | Promise<void>

Implementation of

Server.listen

---

listenerCount()

listenerCount<E>(eventName, listener?): number;

Defined in: node_modules/@types/node/events.d.ts:170

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type	Description
eventName	string | symbol	The name of the event being listened for
listener?	(...args) => void	The event handler function

Returns

number

Since

v3.2.0

Inherited from

EventEmitter.listenerCount

---

listeners()

listeners<E>(eventName): (...args) => void[];

Defined in: node_modules/@types/node/events.d.ts:186

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol

Returns

(...args) => void[]

Since

v0.1.26

Inherited from

EventEmitter.listeners

---

off()

off<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:191

Alias for emitter.removeListener().

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol
listener	(...args) => void

Returns

this

Since

v10.0.0

Inherited from

EventEmitter.off

---

on()

on<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:225

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

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Since

v0.1.101

Inherited from

EventEmitter.on

---

once()

once<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:256

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Since

v0.3.0

Inherited from

EventEmitter.once

---

prependListener()

prependListener<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:275

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Since

v6.0.0

Inherited from

EventEmitter.prependListener

---

prependOnceListener()

prependOnceListener<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:292

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.

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type	Description
eventName	string | symbol	The name of the event.
listener	(...args) => void	The callback function

Returns

this

Since

v6.0.0

Inherited from

EventEmitter.prependOnceListener

---

rawListeners()

rawListeners<E>(eventName): (...args) => void[];

Defined in: node_modules/@types/node/events.d.ts:326

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

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol

Returns

(...args) => void[]

Since

v9.4.0

Inherited from

EventEmitter.rawListeners

---

removeAllListeners()

removeAllListeners<E>(eventName?): this;

Defined in: node_modules/@types/node/events.d.ts:338

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.

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName?	string | symbol

Returns

this

Since

v0.1.26

Inherited from

EventEmitter.removeAllListeners

---

removeListener()

removeListener<E>(eventName, listener): this;

Defined in: node_modules/@types/node/events.d.ts:425

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 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.

Type Parameters

Type Parameter
E extends string | symbol

Parameters

Parameter	Type
eventName	string | symbol
listener	(...args) => void

Returns

this

Since

v0.1.26

Inherited from

EventEmitter.removeListener

---

sendMessage()

abstract sendMessage<T>(pattern, data): Promise<unknown>;

Defined in: packages/microservices/src/transports/server.ts:54

Send a request and wait for the response.

Type Parameters

Type Parameter	Default type
T	unknown

Parameters

Parameter	Type
pattern	string
data	T

Returns

Promise<unknown>

Implementation of

Server.sendMessage

---

setMaxListeners()

setMaxListeners(n): this;

Defined in: node_modules/@types/node/events.d.ts:436

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

Parameter	Type
n	number

Returns

this

Since

v0.3.5

Inherited from

EventEmitter.setMaxListeners

Properties

Property	Modifier	Type	Description	Defined in
eventHandlers	readonly	Map<string, MessageHandler>	Handlers for fire-and-forget event patterns.	packages/microservices/src/transports/server.ts:27
messageHandlers	readonly	Map<string, MessageHandler>	Handlers for request-response patterns.	packages/microservices/src/transports/server.ts:25