How do you close netcat connection after receipt of data?

Question

A very simple use of netcat is below:

#!/bin/sh

echo "hello world" > original.txt
base64 original.txt > encoded.txt
cat encoded.txt | nc -l -p 1234 -q 0

#!/bin/sh

nc localhost 1234 -q 0 > received.txt
base64 -d received.txt > decoded.txt
rm received.txt encoded.txt
echo "Sent:"
md5sum original.txt
echo "Received:"
md5sum decoded.txt
rm decoded.txt original.txt

This creates a file, encodes it into base64, sends it over netcat , and then decodes it, finally comparing whether what was sent and what was received is identical using a checksum comparison.

On a Kali Linux machine I was using earlier, the netcat connection closes upon execution of the second script, but trying on Ubuntu at home, this is not the case. I need to manually close the connection with Ctrl+D .

How can I make it such that the connection closes after receiving this data?

Answer 1

I think including the -c flag for nc should do it. Also, are you sure you want to use Bourne shell, and not Bash? I'd suggest changing your shebang to #!/bin/bash