curl / Mailing Lists / curl-library / Single Mail
Buy commercial curl support from WolfSSL. We help you work out your issues, debug your libcurl applications, use the API, port to new platforms, add new features and more. With a team lead by the curl founder himself.

Send data before receiving data using the callback approach for WebSocket requests

From: Darshan Sen via curl-library <>
Date: Mon, 5 Jun 2023 17:08:58 +0530

Hi! I was experimenting with sending WebSocket requests using libcurl.
Since my codebase already uses the callback approach for HTTP requests and
I was just adding support for WebSocket connections, I thought of
continuing using the same write callback for WebSocket connections too.
However, I was trying to connect with a WebSocket server that expects the
client to send data before responding. So I had a question:

When using the callback approach
is it possible to run curl_ws_send() right after the connection is
established, before the write callback function is executed for the first

It isn't documented but I still tried setting CURLOPT_READFUNCTION to a
valid read callback function but that didn't work, so I guess read
callbacks are not expected to work when doing WebSocket requests. Does this
mean that I would need to use the connect-only approach
for WebSocket connections?

Even if we find a solution for the callback approach, I was wondering if
any of these approaches <> are
recommended over the other?


Received on 2023-06-05