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Introduce GristSocketServer, GristServerSocket and GristClientSocket
These classes, used as an alternative to native WebSockets, provide an automatic fallback to HTTP long polling (implemented using Engine.IO) when a WebSocket connection fails.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,150 @@ | ||
| import WS from 'ws'; | ||
| import {Socket as EIOSocket} from 'engine.io-client'; | ||
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| export interface GristClientSocketOptions { | ||
| headers?: Record<string, string>; | ||
| } | ||
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| export class GristClientSocket { | ||
| private _wsSocket: WS.WebSocket | WebSocket | undefined; | ||
| private _eioSocket: EIOSocket | undefined; | ||
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| // Set to true when the connection process is complete, either succesfully or | ||
| // after the WebSocket and polling transports have both failed. Events from | ||
| // the underlying socket are not forwarded to the client until that point. | ||
| private _openDone: boolean = false; | ||
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| private _messageHandler: null | ((data: string) => void); | ||
| private _openHandler: null | (() => void); | ||
| private _errorHandler: null | ((err: Error) => void); | ||
| private _closeHandler: null | (() => void); | ||
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| constructor(private _url: string, private _options?: GristClientSocketOptions) { | ||
| this._createWSSocket(); | ||
| } | ||
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| public set onmessage(cb: null | ((data: string) => void)) { | ||
| this._messageHandler = cb; | ||
| } | ||
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| public set onopen(cb: null | (() => void)) { | ||
| this._openHandler = cb; | ||
| } | ||
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| public set onerror(cb: null | ((err: Error) => void)) { | ||
| this._errorHandler = cb; | ||
| } | ||
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| public set onclose(cb: null | (() => void)) { | ||
| this._closeHandler = cb; | ||
| } | ||
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| public close() { | ||
| if (this._wsSocket) { | ||
| this._wsSocket.close(); | ||
| } else { | ||
| this._eioSocket!.close(); | ||
| } | ||
| } | ||
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| public send(data: string) { | ||
| if (this._wsSocket) { | ||
| this._wsSocket.send(data); | ||
| } else { | ||
| this._eioSocket!.send(data); | ||
| } | ||
| } | ||
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| // pause() and resume() are used for tests and assume a WS.WebSocket transport | ||
| public pause() { | ||
| (this._wsSocket as WS.WebSocket)?.pause(); | ||
| } | ||
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| public resume() { | ||
| (this._wsSocket as WS.WebSocket)?.resume(); | ||
| } | ||
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| private _createWSSocket() { | ||
| if(typeof WebSocket !== 'undefined') { | ||
| this._wsSocket = new WebSocket(this._url); | ||
| } else { | ||
| this._wsSocket = new WS(this._url, undefined, this._options); | ||
| } | ||
| this._wsSocket.onmessage = this._onWSMessage.bind(this); | ||
| this._wsSocket.onopen = this._onWSOpen.bind(this); | ||
| this._wsSocket.onerror = this._onWSError.bind(this); | ||
| this._wsSocket.onclose = this._onWSClose.bind(this); | ||
| } | ||
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| private _destroyWSSocket() { | ||
| if (this._wsSocket) { | ||
| this._wsSocket.onmessage = null; | ||
| this._wsSocket.onopen = null; | ||
| this._wsSocket.onerror = null; | ||
| this._wsSocket.onclose = null; | ||
| this._wsSocket = undefined; | ||
| } | ||
| } | ||
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| private _onWSMessage(event: WS.MessageEvent | MessageEvent<any>) { | ||
| if (this._openDone) { | ||
| // event.data is guaranteed to be a string here because we only send text frames. | ||
| // https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/message_event#event_properties | ||
| this._messageHandler?.(event.data); | ||
| } | ||
| } | ||
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| private _onWSOpen() { | ||
| // The connection was established successfully. Any future events can now | ||
| // be forwarded to the client. | ||
| this._openDone = true; | ||
| this._openHandler?.(); | ||
| } | ||
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| private _onWSError(ev: Event) { | ||
| // The first connection attempt failed. Trigger an attempt with another transport. | ||
| this._destroyWSSocket(); | ||
| this._createEIOSocket(); | ||
| } | ||
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| private _onWSClose() { | ||
| if (this._openDone) { | ||
| this._closeHandler?.(); | ||
| } | ||
| } | ||
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| private _createEIOSocket() { | ||
| this._eioSocket = new EIOSocket(this._url, { | ||
| path: new URL(this._url).pathname, | ||
| addTrailingSlash: false, | ||
| transports: ['polling'], | ||
| upgrade: false, | ||
| extraHeaders: this._options?.headers, | ||
| withCredentials: true, | ||
| }); | ||
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| this._eioSocket.on('message', this._onEIOMessage.bind(this)); | ||
| this._eioSocket.on('open', this._onEIOOpen.bind(this)); | ||
| this._eioSocket.on('error', this._onEIOError.bind(this)); | ||
| this._eioSocket.on('close', this._onEIOClose.bind(this)); | ||
| } | ||
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| private _onEIOMessage(data: string) { | ||
| this._messageHandler?.(data); | ||
| } | ||
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| private _onEIOOpen() { | ||
| this._openHandler?.(); | ||
| } | ||
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| private _onEIOError(ev: any) { | ||
| // We will make no further attempt to connect. Any future events can now | ||
| // be forwarded to the client. | ||
| this._openDone = true; | ||
| this._errorHandler?.(ev); | ||
| } | ||
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| private _onEIOClose() { | ||
| this._closeHandler?.(); | ||
| } | ||
| } |
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