Checking if cable connected with tcp?

[Riku]

SERVER TO CLIENT CHECK
1. Is there a way using tcp to check if a ethernet cable is plugged in the computer even if computer is shut down.

Or does it need POE and some modules attached on the computer.

CLIENT TO SERVER CABLE DISCONNECTED MESSAGE
2. Other question is if there is a existing hardware module at client end that can send a tcp message when cable is disconected even when computer poweded down.

Solution 2 would be good as there would be minimal network traffic.

F: Riku Tuominen
riku.tuominen@benchmarking.fi

 

[gmail2]

No - there is no way of knowing whether another machine has it's cable connected or not. Likewise there's no way to send anything past layer 1 to say the cable is disconnected ... how would the traffic reach it's destination with no cable to send it over !!!!!?????

Irish Poetry - Karen O'Connor
Irish Poetry and Short Stories - Doghouse Books
Garten und Landschaftsbau

 

[burtsbees]

I think he's saying that a computer that may be trying to communicate with the computer in question cannot reach it and is therefore sending the "cable unplugged" message.
A message like that (especially in Windoze) is very generic---Windoze will say that when the interface is in the wrong subnet, if a driver gets corrupted, if the NIC is faulty, if the router is down (if it's in a different subnet), if a switchport is faulty, etc.).
If the computer is shutdown, it can still have activity on the NIC port with a cable plugged in (at least I know of some servers that can...)...how else could "wake on LAN" work?

Burt

 

[gdvissch]

if your switch is using SNMP, you could send a traps when the cable is diconnected
This will work even if the server/PC is switched off.
The NIC stays powered on (at least on modern hardware and with powermanagement not configured to shut the NIC down)

As soon as the cable is pulled, the switch will see it and send and SNMP Link Down trap to management host (if the switch is configured correctly)

It will never work using TCP only. You couldn't make the difference between a cabled not connected or a routing problem that prevents your local host talking to the remote host

G.