java - how to work out payload size from html5 websocket -

how can tell html5 message payload length on websockets?

im aware base protocol consists of op code, length determine next 1 8 bytes, following values hashing , rest payload!

im creating java serverside application receivea message html5 client , handle, ii can handle messages 256 bytes.

any work out manually great (i.e how habdle bytes determine payload)

cheers

there 3 ways how payload length of websocket frame can encoded, depend on length of payload:

1. 125 or less
2. 126-65535
3. 65536 +

which way used can told looking @ value of 7 last bits of 2nd byte (the first bit of 2nd byte masking flag).

when it's below 126, it's payload length. when it's 126, payload length in following 2 bytes. when it's 127, payload length in following 8 bytes.

so algorithm have follow interpret websocket frame is:

1. read 1st byte ("byte0") fin flag , opcode
2. read 2nd byte ("byte1")
3. when byte1 greater 127, subtract 127 byte1 , set masked true
4. when byte1 126, read next 2 bytes , convert short. payload_length.
5. when byte1 127, read next 8 bytes , convert long. payload_length.
6. when byte1 else, payload_length equal value of byte1
7. when masked true, read next 4 byte. masking_key.
8. read number of bytes have in payload_length payload.
9. when masked true, apply masking_key payload.

there no hash-code in websocket frame, must have mixed up. integrity of websocket frame ensured tcp layer beneath it.

for more information websocket protocol, refer rfc 6455.