Decode a websocket frame

Question

I am trying to decode a websocket frame, but I\'m not successful when it comes to decoding the extended payload. Here what I did achieve so far:

char *in = data;         


        

Answer 1

If packet_length is 126, the following 2 bytes give the length of data to be read.
If packet_length is 127, the following 8 bytes give the length of data to be read.
The mask is contained in the following 4 bytes (after the length).
The message to be decoded follows this.

The data framing section of the spec has a useful illustration of this.

If you re-order your code to something like

• Read packet_length
• Check for packet_length of 126 or 127. Reassign packet_length to value of following 2/4 bytes if required.
• Read mask (the 4 bytes after packet_length, including any additional 2 or 8 bytes read for the step above).
• Decode message (everything after the mask).

then things should work.