[zeromq-dev] PicoTCP ZeroMQ implementation

Toon Peters toon.peters at tass.be
Tue Jan 14 12:19:49 CET 2014

Dear All,

I'm currently trying to improve our ZeroMQ implementation on our TCP/IP
stack called PicoTCP (All the source files can be found at

I'm currently trying to figure out all of the ZMTP 2.0 fields in the
protocol, but I have noticed that some implementations don't really seem to
adhere to the protocol.

example: I'm using the pyzmq library and have one publisher and one
subscriber. Here's what's happening on byte level:

*Sub -> Pub*
Signature: FF 00 00 00 00 00 00 00 01 7F ( the signature mentions 8 times
0x00, while the documentation below mentions 8 octets + 1. Could you
provide any clarification here?
Revision: 01 (= V2.0)
Socket type: 02

Further bytes:
0x00 0x00 (=final short? what does the second byte stand for? length of
0x00 0x01 0x01 (= body? What's the function of the body?)

*Pub -> Sub*
signature: FF 00 00 00 00 00 00 00 01 7F
Revision: 01
Socket type: 01

Further bytes:
0x00 0x00 (=final short? nothing in the body?)
0x00 0x0C [Data] (shouldn't the first byte be 0x01 (more short))

When sending larger chunks of data (> 255 bytes), the data part changed into
0x02 0x00 0x00 0x00 0x00 0x00 0x00 0xAB 0xCD (= more-long ? But the start
byte is not 0x03)

I hope you can clarify some stuff here and there
Thanks in advance!
Toon Peters
*Embedded Software Engineer*

*E toon.peters at tass.be <toon.peters at tass.be> | W www.tass.be
<http://www.tass.be> *

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