Before going to a lot of programming effort; I suggest that you use a packet monitor on the wire to confirm that the data is really in the initial SYN packet. Even Net::RawIP would give you back the packets data.

But one is puzzled why you aren't receiving at least 12(4+8) apparently garbage bytes at the beginning of the first read.

Upon re-reading your message, I don't think the "socket syn data" (line 1) and the "manufacturer, sync packet format" are referring to the same thing . What is the manufactures definition of a "word" and "dword". Try starting with a 12 byte sysread() upon initial accept and then unpack that after determining the byte order (little or big endian).

It is always better to have seen your target for yourself, rather than depend upon someone elses description.