带有node.js的binaryjs的websocket有效负载的开销

Question

I have implemented an application which sends multimedia content via websocket. I've observed, by analysing the traffic with wireshark, that the payload sending the same content with http and websocket differs. For websocket, the payload is always exactly 6 bytes larger than for http. (The headers are obviously completely different, what is clear.)

I implemented it on javascript using Node.js with the module binaryjs on the server.

Either Node.js or binaryjs library adds 5 bytes at the beginning of the multimedia data (it looks like 0x93 0x02 0xda 0x5e 0xcb) and 1 more byte at the end of it (it looks like 0x15). Any idea where this overhead may come from?

Answer 1

As robertklep said the overhead you mention is because of metadata. binarypack which is used by binaryjs in serializing/deserializing (or packing/unpacking) binary data adds those bytes. binarypack uses much of messagepack specs and adds a few extra.

The function likely adding those extra bytes is pack_bin which works for binary files. You can see that here .