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   Author  Topic: Optimization for Slow Links  (Read 4301 times)
Kumar
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Optimization for Slow Links
« on: Oct 20th, 2012, 5:56am »
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Hello,
 
i am trying to set up a remote access to our PLC.  
for that i have an embedded device hard wired to the plc (rs232). the embedded device forwards the rs232 traffic via tcp-rfc2217 to my host machine where i am running Serial Port redirector.
 
the connection to the embedded device is a GSM/UMTS link with RTT between 500-800 ms, sometimes over 2000ms
 
via lan it works perfectly but over the wan link its really slow and the software i am using to access the PLC (codesys) times out so i can only access the plc 3/10 times
 
is there a way to integrate a certain timeout period for each packet in serial port redirector?
 
maybe you can help me with this issue
 
thank you
 
regards
kumar
 
 
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Serge Frost
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Re: Optimization for Slow Links
« Reply #1 on: Oct 22nd, 2012, 7:01am »
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Hello,  
 
Are you familiar with "PortMon" software? I need you to take the logs of your PLC when it works correctly via LAN and when it works via Internet.  
 
I will compare these logs and will try to find the source of the issue.  
 
You can download "PortMon" from Microsoft Official Web Site or from our FTP server:
ftp://castle.colonet.net/upload/support_tools/PortMon/
 
Send these log files to my email: support@fabulatech(dot)com
 
Thanks!
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Kumar
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Re: Optimization for Slow Links
« Reply #2 on: Oct 22nd, 2012, 7:19am »
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Hello,
 
thanks for your fast reply. it seems portmon is not available for windows 7 64 bit systems.
 
see: http://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/portmon-equivalent-for-win-7-64-bit/187c4fe0-2e1c-415b-9c14-3e65f9901fb5
 
do you have an alternative?
 
thank you
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Serge Frost
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Re: Optimization for Slow Links
« Reply #3 on: Oct 22nd, 2012, 7:55am »
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Yes, unfortunately it doesn`t work on 64-bit systems.Ok, lets do it in another way.  
 
Here is the link for downloading HyperTerminal:
 
ftp://castle.colonet.net/upload/support_tools/HyperTerminal/
 
Download it on two computers and transfer a big file (>5 Mb) via Internet. And let me know the results of this little test.
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Kumar
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Re: Optimization for Slow Links
« Reply #4 on: Oct 22nd, 2012, 8:27am »
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i am really sorry, but unfortunately i dont have any gprs modem available to insert the simcards i am using for my embedded linux devices (they already have the modem built in)
 
is there anything else i can test?
 
i am looking for a setting to make the virtual port reliable even with high rtt's (400-1000ms)
 
e.g. com0com offers:
AddRTTO=<n> - add <n> milliseconds to the total time-out period for read operations (0 by default)  
AddRITO=<n> - add <n> milliseconds to the maximum time allowed to elapse between the arrival of two characters for read operations (0 by default)
 
maybe you have something similar or even better?
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Serge Frost
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Re: Optimization for Slow Links
« Reply #5 on: Oct 25th, 2012, 5:57am »
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Hi,
 
I tried to reproduce this issue. I set bandwidth to 9,6 kB with the help of NetLimiter and tried to work with Serial Port Redirector.  I was working slowly but it worked.  
 
Ok, is it possible to get "WireShark" logs? (http://www.wireshark.org/) It is freeware and it works on all computers with all operating systems. I need logs when it works correctly in local network and when it works via internet. I will compare these logs and will try to find the source of the issue. Also please let me know your IP addresses and the number of TCP port in Serila Port Redirector so I can configure filters in WireShark.  
 
One more questions. What is the speed of COM port opening in codesys?
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