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I have a device that connect to a Window PC by LAN cable directly instead of serial port. Back when I use serial port, I can use coolterms or hyperterminal program to read the exact data send in from the serial port (as COM port on the computer). But now the device has changed its data transfer to a LAN cable. How can I read the data? Are there similar program like hyperterminal that reads ethernet data?

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What is the device you are referring to? – Mark Johnson Jan 5 '12 at 2:29
It is a custom laser device that has a separate controller that contains a touch monitor. The LAN terminal from the device basically send some text and images to the PC through LAN cable. – KMC Jan 5 '12 at 2:35
You need a LAN sniffer. In some cases you can use a standard computer with a special program, though the LAN adapter in the computer must be able to operate in "promiscuous" mode where it reads all traffic. But keep in mind that the traffic to the device is likely very complex, and will be hard to decipher even after you've gotten it dumped out. – Daniel R Hicks Jan 5 '12 at 3:15
i search online and where's only wireless sinffer, no LAN sniffer. I do not know the IP of the device. How to I connect the device to the computer and start "sniffing" like we do for serial port? – KMC Jan 5 '12 at 6:37
Install Wireshark and let it sniff in promiscuous mode. – slhck Jan 5 '12 at 9:25
up vote 0 down vote accepted

Are both devices connected to a network? If you can find the IP address, try "COM Port Data Emulator." Allows you to put your computer in TCP/IP server mode and send data through ports on ethernet.

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I would try a Cisco compatible console adapter: This has an rj45 female port to connect to your lan cable and a female rs232 connector to connect your your serial port. You can then use a program such as hyper terminal to pull the data off.

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