Issue with Websocket+TLS in Poco 1.13.3

[acarioni]

Issue with Websocket+TLS in Poco 1.13.3

[matejk]

In the example shown above there is only one WebSocket instantiated and then used in reader and writer inside the same process. Reader wants to read data using ::SSL_read in function receiveBytes and writer wants to send the data using the same instance of websocket (sendBytes).

Mutex to protect SSL members is locked by reader and therefore the writer can't send.

I doubt that this is a valid use case at all. Reader and writer shall have their own instances of web socket and not share the same one. @aleks-f ?

[acarioni]

To clarify, my project involves a WebSocket client that is designed to be receptive to messages from the server at any moment. Given this requirement, it's practical to have a dedicated thread constantly monitoring the WebSocket connection for incoming data. Further, the same client must be capable of sending messages at any time, as it interacts with user-generated input. This design rationale underpins the structure of my code example, which I hope is now more understandable.

The scenario I've described is typical for applications that produce and consume real-time data and the straightforward implementation I've provided is effective when using a plain WebSocket. Problems arise when I try to use a Secure WebSocket because reading from the WebSocket prevents any writing.

[matejk]

@acarioni , would it be possible for you to have two instances of websockets: one for reading and another completely independent for writing to the server?

[acarioni]

Do you mean two Websocket connections, one for reading and one for writing, or two Websocket objects sharing the same connection?

In my case, the first alternative is not acceptable but the second one is.

[matejk]

Having two Websocket objects would definitely solve locking issue. Is it possible for you to test whether it work properly on one connection in your situation?

[acarioni]

After implementing the suggested changes, the program still hangs.

The reason is that both ws and ws2 (see the code below) reference the same SecureSocketImpl instance. Consequently, this shared instance's mutex becomes a contention point, as it is simultaneously accessed by SecureSocketImpl::receiveBytes and SecureSocketImpl::sendBytes.

  // same as before ...
  WebSocket ws(cs, request, response);
  WebSocket ws2(ws);

  Reader rdr(ws);
  Poco::Thread tr;
  tr.start(rdr);

  Writer wrt(ws2);
  Poco::Thread tw;
  tw.start(wrt);

  tr.join();
  tw.join();

[aleks-f]

@acarioni what you are doing is not thread-safe, you can't safely access the same SSL object from multiple threads:

openssl/openssl#20446 (comment)

You should decouple those threads with notification queues and do the I/O in one thread only.