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Does anyone know a device which has Ethernet port to act as an adapter between a TCP client and a server, with the purpose to intercept data? It has to have the ability to receive data from one side and send it to the other with the extra ability to send data also on one additional IP/port. That port should be read-only.

The similar device which converts data between serial and TCP which I know exist is MOXA NPort. They call it Serial Device Server.

I would appreciate also if you can tell me if there is a programmable device which has Ethernet connector.

UPDATE: It isn't necessary for the client and the server to be directly connected to each another. They both can maintain separate connection with the adapter, so that adapter would be a server/client with additional read-only connection on the server side. In that case it is effectively a computer connected to the router. As a programmer I know that it can be achieved using a PC with a simple software, but a would prefer a dedicated hardware.

Elvedin Hamzagic
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1 Answers1

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1. Network switch TAP port

On a switch, the read-only port is often called a "TAP" port...

enter image description here

https://observer.viavisolutions.com/includes/popups/taps/tap-vs-span.php

...although different vendors have different names.

This will pass you all the data that goes bettwen the two devices, but the switch essentially reads the incomming packets and then retransmitts them out the TAP port, so the data is buffered and error checked by the switch. You may not see some kinds of packets (like runts or bad CRC), and the timing of the packets will be altered because of the buffering.

2. Dedicated tap hardware

These are expensive, but typically give you lower level access to the data. This is good if, say, you need exact timestamps for the packets which are not available on a switch TAP port becuase the packets are buffered.

enter image description here

http://datacomsystems.com/products/network-taps

3. Passive hardware tap

If you can get both devices to run at 10Base-T speeds, you can use a passive tap like this one...

enter image description here http://hackerwarehouse.com/product/lan-tap-pro/?gclid=COGQ7Y3yqtACFdRMDQodYH4CKg

They are also not hard to make yourself if you have the right tools. A passive tap can show you even media level problems which don't usually show up on the higher level taps.

Community
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  • Thanks @bigjosh. I will consider your proposals. I've updated my question to be more specific on what I need. –  Nov 15 '16 at 14:48