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#### async_detect_ssl

Detect a TLS/SSL handshake asynchronously on a stream.

##### Synopsis

Defined in header `<boost/beast/core/detect_ssl.hpp>`

    template<
        class AsyncReadStream,
        class DynamicBuffer,
        class CompletionToken = net::default_completion_token_t<beast::executor_type<AsyncReadStream>>>
    DEDUCED
    async_detect_ssl(
        AsyncReadStream& stream,
        DynamicBuffer& buffer,
        CompletionToken&& token = net::default_completion_token_t< beast::executor_type< AsyncReadStream > >{});

##### Description

This function reads asynchronously from a stream to determine if a client handshake message is being received.

This call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:

- A TLS client opening handshake is detected,
- The received data is invalid for a TLS client handshake, or
- An error occurs.

The algorithm, known as a composed asynchronous operation, is implemented in terms of calls to the next layer's `async_read_some` function. The program must ensure that no other calls to `async_read_some` are performed until this operation completes.

Bytes read from the stream will be stored in the passed dynamic buffer, which may be used to perform the TLS handshake if the detector returns true, or be otherwise consumed by the caller based on the expected protocol.

##### Parameters

Name | Description
--- | ---
`stream` | The stream to read from. This type must meet the requirements of AsyncReadStream.
`buffer` | The dynamic buffer to use. This type must meet the requirements of DynamicBuffer.
`token` | The completion token used to determine the method used to provide the result of the asynchronous operation. If this is a completion handler, the implementation takes ownership of the handler by performing a decay-copy, and the equivalent function signature of the handler must be:
    void handler(
        error_code const & error,    // Set to the error, if any
        bool result                 // The result of the detector
    );
If the handler has an associated immediate executor, an immediate completion will be dispatched to it. Otherwise, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using `net::post`.