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| author | Martin Sustrik <sustrik@250bpm.com> | 2010-03-10 12:40:13 +0100 |
|---|---|---|
| committer | Martin Sustrik <sustrik@250bpm.com> | 2010-03-10 12:40:13 +0100 |
| commit | 8f90ae8dfdf5efbb6c8429897dc95cad621af00b (patch) | |
| tree | c0ff240ca45d39c09032d35507c7229e876c8d40 /doc/zmq_pgm.txt | |
| parent | 98801ebcaea1117ae596a3bae0653c3720a94359 (diff) | |
wire formats in docs clarified
Diffstat (limited to 'doc/zmq_pgm.txt')
| -rw-r--r-- | doc/zmq_pgm.txt | 40 |
1 files changed, 31 insertions, 9 deletions
diff --git a/doc/zmq_pgm.txt b/doc/zmq_pgm.txt index c92824e..ffbe9bd 100644 --- a/doc/zmq_pgm.txt +++ b/doc/zmq_pgm.txt @@ -81,20 +81,42 @@ order specifying either the offset of the first message 'frame' in the datagram or containing the value 0xFFFF if the datagram contains solely an intermediate part of a larger message. -A single PGM datagram as used by 0MQ can thus be defined by the following ABNF -grammar: +The payload of a single PGM datagram as used by 0MQ can thus be defined by the +following ABNF grammar: .... -datagram = message / intermediate -message = (frame-offset *data 1*frame) <1> -intermediate = (escape 1*data) -frame-offset = 2OCTET -escape = %xFF %xFF -data = 1*OCTET +datagram = (offset data) +offset = 2OCTET +data = *OCTET .... -<1> 'frame' as defined in linkzmq:zmq_tcp[7]. +As already explained above, the data from consecutive datagrams are interpreted +as a bytestream that's parsed according to the grammar described in +linkzmq:zmq_tcp[7]. +Each packet thus looks like this: + +---- ++-----------+------------+------------------+----------------------+ +| IP header | PGM header | offset (16 bits) | data | ++-----------+------------+------------------+----------------------+ +---- + +Following example shows how messages are arranged in subsequent packets: + +---- ++---------------+--------+-----------+-----------------------------+ +| PGM/IPheaders | 0x0000 | message 1 | message 2 (part 1) | ++---------------+--------+-----------+-----------------------------+ + ++---------------+--------+-----------------------------------------+ +| PGM/IPheaders | 0xFFFF | message 2 (part 2) | ++---------------+--------+-----------------------------------------+ + ++---------------+--------+--------------------------+-----------+ +| PGM/IPheaders | 0x0008 | message 2 (last 8 bytes) | message 3 | ++---------------+--------+--------------------------+-----------+ +---- EXAMPLE ------- |