Does a router tells a device to close a TCP connection?

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Discussion Overview

The discussion revolves around the behavior of routers in relation to TCP connections, specifically whether a router informs a slave device to close a TCP connection if it loses connection with a master device. The context includes practical applications involving a Qterm-g72 HMI and a Moxa device over TCP Modbus, exploring connectivity issues when a router or computer is involved.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a router tells a slave device to close a TCP connection if it loses connection with the master device, seeking clarification on the role of routers in this context.
  • Another participant asserts that routers do not provide functionality beyond routing packets and questions the assumption that a router could instruct another device to close a port.
  • A different participant mentions issues with Moxa Nport devices and asks for clarification on whether the connection works without the router or not at all.
  • One participant notes that their router allows for automatic disconnection based on idle time, suggesting that some routers have features that may affect connectivity.

Areas of Agreement / Disagreement

Participants express differing views on the functionality of routers, with some asserting that routers do not manage TCP connections while others suggest that certain router features could influence connectivity. The discussion remains unresolved regarding the specific behavior of routers in this scenario.

Contextual Notes

There are limitations regarding the specific models of Moxa devices mentioned and the exact nature of the connectivity issues, which are not fully explored. The discussion also lacks clarity on the assumptions about router capabilities and the conditions under which the HMI and Moxa operate.

btb4198
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Does a router tells a slave device to close a TCP connection, if the router loses connect from the master device ? So, I have a Qterm-g72 HMI and I am trying to connect it to a Moxa over TCP Modbus. This only works if a Computer or a router is between the Moxa and the HMI. I am trying to found out why. So, my question is does a computer or a router close the connection to the Moxa if it lose it from the HMI ? The HMI is the master so it does the talking and the Moxa is the slave. The Moxa does not know to lost the connection if the HMI does not tell is to close with TCP, so I wanted to know if the Computer or Router would do that ?
Also does anyone else think they might know why the HMI and the Moxa will not work with a router or a computer in between?
 
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Which Moxa device are you using?
We had some serious issues with the Moxa Nport devices and Modbus.

But no a router doesn't provide any functionality other than routing the packets between device.

When you don't have the router installed does it work at all and then stop? Or just not work period?
Have you tried using a cross over ethernet cable?
 
@cpscdave Is correct. routers simply take packets and move them around. What makes your think a router is 'telling' some other network object to close a port? Routers are really dumb - they simply filter stuff, and sometimes drop what they have been instructed to - as bad packets. None of this explicitly requests a 'close operation' on anything that I know of.
 
Mine allows an automatic internet disconnection depending on idle time and a dayly forced shutdown (with probably an automatic restart.)
 

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