I want a simple way to show all the TCP data (not the TCP headers or anything else) going over any interface on my Linux box.
For instance, I want a magical command that if I do:
magic_commmand_I_want port=1234
then if there was a server listening on port 1234 on my machine, and someone did:
echo hello | nc localhost 1234
# Note: "nc" (aka "netcat") is a simple tool that sends data to a host/port
Then the magical command would just print out:
hello
I've tried "tcpdump", "ethereal", "tethereal", "tshark", and others, but it isn't obvious how you get them to:
- not show IP addresses or other metadata
- only show the "data" being sent, not individual packets and their headers
- print the data as-is, not in hex, and not with packet-offset markers
- sniff all network traffic (whether it's on eth0 or eth1 or lo, etc...)
Yes, you could probably string together a piped set of unix commands to do this, but that isn't very easy to remember for next time :)
If you have a simple example of an exact command-line that does this, that's what I'd like.
Answer
Update:
As pointed by Michal in the comments: From tcpflow version 1.3 the -e option is used for specifying the scanner name. So the error "Invalid scanner name '8983'" is printed. The correct command is
sudo tcpflow -i any -C -J port 1234
(also -J
has been changed to -g
in the latest release)
Thanks to yves for pointing me to "tcpflow". Here's the commmand-line:
tcpflow -i any -C -e port 1234 # as root, or with sudo
This does everything I want
- displays the data byte-for-byte as it comes in
- doesn't display any other metadata
- listens on all interfaces (so it captures data coming from within the machine and outside)
The "-C
" tells it to dump to the console instead of a file. The "-e
" enables colors so client->server and server->client are visually distinct.
I installed tcpflow by simply doing
sudo apt-get install tcpflow
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