In most frameworks, continuation frames are handled automatically - since actix web has a "do it yourself" methodology, it's not.

I'd recommend reading this, since it has a good overview of the entire formal protocol as well as continuation frames: https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_servers

again, though, continuation frames are only required if you're sending very large messages though web sockets (like files). You can instead have the server send something to the client like {"message": "upload the file, please!"} and then have the client do

if (message.message === "upload the file, please!"}

httpClient.post("/fileUploadEndpoint", myFile)

which completely circumvents the requirement for handling continuation frames.

In short you have three options:

1. use the post method detailed above

2. handle continuation frames (also has the nice benefit of supporting other large messages)

3. switch frameworks to one where continuation frames are handled by default (most mainstream frameworks handle this out of the box)

Good luck!