Like most replies I've seen from TAG Heuer "tech support", what Marcus wrote is complete bullshit. TH always blame the application software or the PC or the power or the weather, because of course their own engineering is always perfect...according to them.
Same type of non-reply we got from TH when SIX of their start clocks croaked in the first 3 days of the World Alpine Championships, back in the day.
The fact remains that the "TCP Sequence Not Expected" error message appears spuriously on the 540 even when the application software is only listening (i.e. not sending "this sent back by your computer" at all).
Other common error messages spewed by the TCP/IP itfc on the 540 are:
"eth frm1 error"
and
"tcp frame re-send"
It's not my job to diagnose TH's hardware problems, but as far as I can determine, the majority of the instability in the 540's TCP/IP stack stems from poor connection timeout housekeeping. The nature of TCP/IP's "stateless" connection requires careful attention to timeout recovery, as network connectivity comes and goes. The 540's firmware does not handle this properly. If you test this carefully, you can get one TCP/IP client to use up all four of the 540's available socket connections (as each goes dead in sequence) until the 540 will not accept any further connex.
As I stated in my previous post, my tests with the 540 have shown it to be stable and perfectly adequate when used as a serial device. If you really need to connect via TCP/IP, then I recommend you use a properly-engineered TCP/IP -> serial converter connected to the 540 via serial. And, of course, be sure you have a spare RJ-11 -> DB9 cable handy, as TH's horrible choice of RJ-11s will cause problems when the little plastic tab snaps off in the cold.
But of course nobody would ever use this product in cold weather.