Dave. Apart from packet dumps, could you get the following:
Output from LCP SHO CHA on the RSX system.
Output from SHOW PORT on the Lantronix
Output from SHOW SYSTEM on Lantronix.
Output from SHOW KNOWN SERVICES on Lantronix.
And if the Lantronix use different commands, I hope you can figure out 
what the equivalent commands would be.
And also, if connected (as in RSX shows the port as connected), the 
output from DEV TTn: on RSX, where TTn: is whatever terminal is 
indicated as connected.
You could also try a BRO TTn: FOOBAR, to see if output to the port works.
   Johnny
On 2025-10-26 04:56, Dave McGuire wrote:
  On 10/25/25 23:46, Tony Nicholson wrote:
          Hi folks, has anyone here used aLantronix
ETS-series or similar
     terminal server for LAT connections to RSX?  We're having a strange
 I have a Lantronix ETS8P running software version V3.6/5(010208)
 that I use to bridge various RS-232 serial devices to LAT services
 on OpenVMS, RSX-11, RSTS/E etc.
 I don't see any issues to any of my machines (and I have a few older 
 images
 that can be MOP downline loaded to the Lantronix if you need them for
 V3.5/9, V3.6/1, V3.6/4) 
 
    Hi Tony.  We use them much as you do, with local services to system 
 consoles as well as for terminals and printers.  They've been working 
 very well for us since we migrated to them recently from a set of 
 DECservers.
 
    I typed this up for Johnny a couple of hours ago so I'll just paste 
 it here:
 
    We have three Lantronix ETS-series terminal servers on the network; 
 we just replaced four DECserver-300s with them.  They are performing 
 great and give us some additional functionality that we wanted.
 
    But we have hit one snag that is just...weird.  Either of the two 
 RSX-11M-PLUS machines that we've tried (an 11/70 and an 11/53) both do 
 this.  From one specific terminal server, when we connect to the LAT 
 service, it gets a connection (and LCP shows it as connected) but there 
 is no login prompt.  It is completely unresponsive.
 
    The other two terminal servers work just fine, and other machines 
 (several VAXen, two Linux machines, etc) can connect to that LAT service 
 just fine, meaning we get the ">" immediately and can log in.
 
    The configurations of the terminal servers are identical. The only 
 difference is that the one with the problem is a 32-port unit and the 
 two that work are 16-port units.
 
    Connections to any other service from the affected terminal server 
 work fine, including connections to RSTS/E on the very same PDP-11s. 
 (most of our machines are set up with multiple system disks for 
 different OSs)
 
    The next time we work on this, possibly next week, we're going to do 
 some packet captures.
 
    Do you have any thoughts on this?
 
             -Dave
  
-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt(a)softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol