set -x # ask the shell to print out what is going on

# This is a simple script that demonstrates ‹nc› in listening mode.
# To wit:

port=2222
nc -l $port > file.txt &

# Now unlike most of the things we did earlier, you may not be able
# to run this script. That's because port numbers are a global,
# shared resource, and if one person is listening on port 2222 on
# ‹aisa›, this port is no longer available for others. You may want
# to try with a different port number (must be greater than 1024,
# too). But since the script is brief, you might get lucky.

# Now let's send something to the listening ‹nc› using another ‹nc›,
# this time in client mode:

echo "hello world on port $port" | nc localhost $port

# ‹localhost› is a special name, reserved to mean ‘this computer’.
# But we could have used ‹aisa.fi.muni.cz› just fine, too. Anyway,
# let's check the content of file.txt:

wait # wait for the backgrounded ‹nc -l› to finish
cat file.txt # print the content of the file

# Let's do another exercise: ‹2.txt›.