08-21-2008
Thank you! The first one is good. I tried "netcat examples" and so on..
I worked out a solution for my task (script that behaves as finger utility) that uses netcat this way and I need to know if the solution is good or not :-(
================================================
Script server-finger.sh still runs and waits for requests from clients. It uses indefinite loop:
================================================
while true ; do
echo "[Waiting for request]"
echo -n "" >"request.file"
nc -l -p 40017 >"request.file" # here it listens for requests
if [ -s "request.file" ]; then
# now we send information via netcat back
echo "[Sending output for request: $user]"
DO_SOME_STAFF >"output.file"
nc -w 1 "$remote_host" "$port"<"output.file"
echo "[Request ($user) was served.]"
fi
done
===============================================
Client script
===============================================
# retrieve IP address of this machine
thisMachine=$(echo `/sbin/ifconfig eth0 | grep "inet addr" | cut -d ":" -f 2 | cut -d " " -f 1`)
host=$(echo $1 | cut -d'@' -f 2)
port=40017
data="SOME DATA TO SEND"
# send data
echo "$data|$thisMachine" | nc -w 1 "$host" "$port"
exitCode=$?
if [ $exitCode -eq 0 ]; then
# wait for data
nc -l -p "$port" >"output.file";
fi
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LEARN ABOUT DEBIAN
safe_finger
SAFE_FINGER(8) Linux Programmer's Manual SAFE_FINGER(8)
NAME
safe_finger - finger client wrapper that protects against nasty stuff from finger servers
SYNOPSIS
safe_finger [finger_options]
DESCRIPTION
The safe_finger command protects against nasty stuff from finger servers. Use this program for automatic reverse finger probes from the
tcp_wrapper (tcpd) , not the raw finger command. The safe_finger command makes sure that the finger client is not run with root privileges.
It also runs the finger client with a defined PATH environment. safe_finger will also protect you from problems caused by the output of
some finger servers. The problem: some programs may react to stuff in the first column. Other programs may get upset by thrash anywhere on
a line. File systems may fill up as the finger server keeps sending data. Text editors may bomb out on extremely long lines. The finger
server may take forever because it is somehow wedged. safe_finger takes care of all this badness.
SEE ALSO
hosts_access(5), hosts_options(5), tcpd(8)
AUTHOR
Wietse Venema, Eindhoven University of Technology, The Netherlands.
Linux 21th June 1997 SAFE_FINGER(8)