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https://github.com/davidje13/echochamber

WebSocket echo chamber server
https://github.com/davidje13/echochamber

nodejs websocket

Last synced: 27 days ago
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WebSocket echo chamber server

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README 

        
# WebSocket Echo Chamber



Low-overhead implementation of a WebSocket communication hub.



Chambers are identified by URL. All connections to the same chamber

will hear each other's messages reflected back and be notified when

connections are made and closed.



## Usage



```sh

npm start [ []]

```



If `domain` is specified, the `Origin` header will be checked against

it. It should be a comma-separated list of permitted domains.



Example allowing local access during development:



```sh

npm start 8080 file://

```



You can include this in another project using npm:



```sh

npm install --save websocket-echo-chamber

```



Once added, you can start the server from the command line:



```sh

echo-chamber 8080 file://

```



Or create your own server programmatically:



```javascript

const {EchoChamberHalls, WebSocketServer} = require('websocket-echo-chamber');



const domains = [];



// Max memory usage is approximately (bytes):

// (MAX_QUEUE_DATA + HEADERS_MAX_LENGTH) * CHAMBER_MAX_CONNECTIONS * MAX_CHAMBERS

// + some overhead from data structures

// Memory usage will typically be much lower (unless explicitly attacked)

// The values below result in ~0.25GB peak memory usage



const echoChamber = new EchoChamberHalls('/', domains, {

	MAX_QUEUE_ITEMS: 1024,

	MAX_QUEUE_DATA: 16 * 1024,

	HEADERS_MAX_LENGTH: 1024,

	CHAMBER_MAX_CONNECTIONS: 64,

	MAX_CHAMBERS: 256,

});



// 2-person echo chambers do not require a queue, so we can support more of them

const p2EchoChamber = new EchoChamberHalls('/p2/', domains, {

	MAX_QUEUE_ITEMS: 0,

	MAX_QUEUE_DATA: 0,

	HEADERS_MAX_LENGTH: 1024,

	CHAMBER_MAX_CONNECTIONS: 2,

	MAX_CHAMBERS: 512,

});



new WebSocketServer()

	.addHandler(p2EchoChamber)

	.addHandler(echoChamber)

	.listen(8080, '127.0.0.1')

	.then((server) => server.printListeningInfo(process.stdout));

```



## Protocol



Connect to a chamber with:



```javascript

socket = new WebSocket(baseURL + chamberName, ['echo']);

```



All received messages will begin with colon-separated metadata. Each

item begins with a letter which denotes its type, followed by

type-specific data. The metadata types are:



* `I`: received when first connecting; gives the unique ID for this

  connection

* `H`: "hi" received when a connection is made

* `B`: "bye" received when a connection is closed or lost

* `F`: "from" the message which follows came from the noted

  connection

* `X`: "truncated" the preceeding message was truncated



After all metadata, there may be a newline followed by an arbitrary

message. If there is no metadata, the message will start with a

newline.



All sent messages will have metadata attached and be distributed to all

other connections (excluding the one which sent the data).



User IDs are currently numeric, but may change to UUIDs or any

alphanumeric format in the future.



See the sources in `test-client` for an example.



### Example server-to-client messages:



#### Begin connection to new room



New connection is assigned ID "100"



```

I100

```



#### Begin connection to existing room



Room already contains "3" and "22", new connection is assigned ID "29"



```

I29:H3:H22

```



#### Message received



Message sent from connection "19"



```

F19

Message here

(may contain extra newlines)

```



#### Partial message received



Message sent from connection "22" but connection is lost before all

data is uploaded, or another data stream forced this one to close



```

F22

Partial messa

```



```

X

```



(the first message appears to complete normally, but is immediately

followed by a header-only message showing the error - `X` = previous

message truncated)



### Example client-to-server messages:



#### Send message to all connections except self



```



Message here

```



#### Send message to any arbitrary connection except self



(will favour long-lived connections which are currently idle)



```

T*

Message here

```



#### Send message to all connections including self



```

T**

Message here

```



#### Send message to specific connection(s) (can include self)



Send to connection "22" and "18"



```

T22,18

Message here

```