How can I adapt Dart's server websocket implementation to work with Phantom 1.9.7 headless browser, given its different websocket standard?

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1

I have encountered an issue while trying to implement websocket support for a Dart server that works with Phantom 1.9.7. The documentation for the WebSocketTransformer indicates it adheres to the RFC6455 standard for upgrading HttpRequests. However, PhantomJS seems to be using an outdated websocket standard. When I attempt to connect to my server, I receive faulty upgrade requests since PhantomJS uses different headers such as sec-websocket-key1 and sec-websocket-key2. Could anyone suggest how I might modify my Dart server code to successfully handle these websocket connections from PhantomJS? Additionally, I noticed that the upgrade method in WebSocketTransformer accepts an optional protocol selector; could this be of any use in resolving this issue?

2

PhantomJS 1.9.7 uses the older Hixie-76 protocol for websockets. Dart's default WebSocketTransformer supports RFC6455, so you'll need custom handling for Hixie-76. Unfortunately, you can't use protocolSelector for this.

To adapt your Dart server, you'll need to manually handle the opening handshake for Hixie-76 and construct a compatible response. However, consider switching to a headless browser supporting modern websocket standards like using Puppeteer with Chrome, as it simplifies handling.

3

Adapting your Dart server to support PhantomJS' Hixie-76 protocol is indeed challenging as it differs significantly from the RFC6455 standard.

Here's a practical way to address the problem:

  • Create a custom middleware function in your Dart server to detect incoming requests needing the Hixie-76 protocol. This will involve checking for the presence of headers like sec-websocket-key1 and sec-websocket-key2.
  • Manually craft the response to meet the Hixie-76 handshake requirements. This will likely involve computing the correct 16-byte response to the key fields and returning a proper HTTP response.
  • Integrate the custom handling logic before the usual RFC6455 processing in your server setup.

Here’s the kicker: upgrading your environment is advisable. Moving to a tool like Puppeteer that supports after RFC6455 standards will drastically reduce long-term maintenance complexities and enhance overall efficiency. Adjusting for outdated protocols can be time-consuming without clear benefits.

While it's technically possible to support the Hixie-76 protocol, sometimes practical efficiency and forward compatibility should guide your decisions.

4

Handling the Hixie-76 protocol used by PhantomJS 1.9.7 on a Dart server requires a workaround as it significantly predates the RFC6455 standard. Here’s how you might approach it:

Custom Handshake Implementation: You'll need to develop a custom solution for handling the handshake. The sec-websocket-key1 and sec-websocket-key2 headers are critical here. Dart does not provide native support for this protocol in WebSocketTransformer, so a pure Dart solution would involve manually parsing the HTTP upgrade request.

To manage this:

  • Identify requests requiring Hixie-76: Implement a middleware that inspects incoming headers for sec-websocket-key1 and sec-websocket-key2. This will help differentiate between the requests needing custom handling versus those using RFC6455.
  • Compute response: You'll need to calculate a response to these keys, which involves complex bitwise operations to generate a valid key3 from key1 and key2 according to the Hixie-76 handshake process.
  • Serve the handshake response: Construct and send back a valid HTTP upgrade response, which might include combining the hash from the key calculation into the HTTP headers correctly.
const server = await HttpServer.bind('localhost', 4040);
server.listen((HttpRequest request) {
  if (_isHixie76Request(request)) {
    _handleHixie76Upgrade(request);
  } else {
    WebSocketTransformer.upgrade(request);
  }
});

bool _isHixie76Request(HttpRequest request) {
  return request.headers.value('sec-websocket-key1') != null &&
         request.headers.value('sec-websocket-key2') != null;
}

void _handleHixie76Upgrade(HttpRequest request) {
  // Implement your key calculations and response here.
}

Advice for Future Compatibility: Although it’s feasible to implement support for Hixie-76 manually, consider upgrading to a headless browser like Puppeteer that adheres to modern standards. This will simplify your development process significantly and spare you the complexities associated with maintaining outdated protocols. Efficient resource utilization and system longevity should direct such technical decisions.