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websocket::stream::async_accept_ex (3 of 3 overloads)

Start responding to a WebSocket HTTP Upgrade request.

    class Body,
    class Allocator,
    class ResponseDecorator,
    class AcceptHandler>
    http::request< Body, http::basic_fields< Allocator >> const& req,
    ResponseDecorator const& decorator,
    AcceptHandler&& handler);

This function is used to asynchronously send the HTTP response to an HTTP request possibly containing a WebSocket Upgrade request. The function call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:

This operation is implemented in terms of one or more calls to the next layer's async_write_some functions, and is known as a composed operation. The program must ensure that the stream performs no other operations until this operation completes.

If the stream receives a valid HTTP WebSocket Upgrade request, an HTTP response is sent back indicating a successful upgrade. When the completion handler is invoked, the stream is then ready to send and receive WebSocket protocol frames and messages. If the HTTP Upgrade request is invalid or cannot be satisfied, an HTTP response is sent indicating the reason and status code (typically 400, "Bad Request"). This counts as a failure, and the completion handler will be invoked with a suitable error code set.





An object containing the HTTP Upgrade request. Ownership is not transferred, the implementation will not access this object from other threads.


A function object which will be called to modify the HTTP response object delivered by the implementation. This could be used to set the Server field, subprotocols, or other application or HTTP specific fields. The object will be called with this equivalent signature:

 void decorator(
    response_type& res


Invoked when the operation completes. The handler may be moved or copied as needed. The equivalent function signature of the handler must be:

 void handler(
    error_code const& ec    // Result of operation

Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using boost::asio::io_context::post.