So then bytes 3 and 4 should be that 16-bit payload length — and this is where things fall apart. The ws message says we have 126 bytes (00000000 01111110) of payload. That sounds plausible. The undici message says we have 25,888 bytes (01100101 00100000) of payload … in a 222 byte packet? Yeah: this one is fishy.

source: HN