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I am looking for a way to view data being transmitted over a TCP port between two computers.

Is there a software package that allows this? I suppose I could script something to re-route data coming in on one port to another and save the data, but there must be something out there already that can do this. Is there something free?

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up vote 6 down vote accepted

Linux / Windows + Cygwin

tcpdump tcp

Linux Gui / Windows


For a specific port (80 for example):

tcpdump tcp port 80

for incoming trafic to port 80

tcpdump tcp dst port 80

Serial port sniffer: click

and : click

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Thanks, I will give Wireshark a try. – Richard Jul 31 '12 at 12:08
wireshark will show you lots and lots of output by default. But once you will notice the connection you want to examine, select it, right click on it and choose 'follow tcp stream' - this will show you all communication between two computers if the packets are captured sequentially. – mnmnc Jul 31 '12 at 12:11
do you know of a similar program for dealing with comports? – Richard Jul 31 '12 at 13:51
Sure i do. Take a look at this: and here: – mnmnc Jul 31 '12 at 13:53

TCPView from SysInternals is a great GUI program that will give you pretty much all of the information you could ever want on your computer's network connection.

This app is for Windows only, however.

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