Sending text file contents to server using netcat?

Question

There is a daemon process listening on port 5144, which I cannot to modify.

I want to use netcat to send the contents of a text file to the server, but this causes netcat to hang the terminal until I press Ctrl+C:

cat file.txt | nc -u 127.0.0.1 5144

The only way I am able to get it to work is by running nc -u 127.0.0.1 5144 and copy/pasting the contents of the file manually.

Any ideas?

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Also note:

1. cat file.txt | ... leads to bash: ...: command not found and I can continue to use the terminal
2. using nc -u 127.0.0.1 5144 < file.txt leads to the same behavior as using | above

Answer 1

If you are using the GNU version of netcat then you can use the -c flag to close the connection on EOF.

-c, --close close connection on EOF from stdin

If you are using the original version of the tool then you can use the -q flag.

-q secs quit after EOF on stdin and delay of secs

An example for the original version is:

cat file.txt | nc -u -q 0 127.0.0.1 5144

I have add "-q 0" to your original command. This closes the connection after the file has been sent.

Answer 2

Assuming that after sending EOF connection will stay idle, you can use -w timeout option, which works for timeout being equal to zero (unlike stupid -q option...)

cat file.text | nc -u localhost 4300 -w0

Answer 3

If you are transferring from FreeBSD to Windows:

FreeBSD: cat file.txt | nc -N 10.0.0.5 5144

-N will shutdown the network socket after EOF

Windows: nc -l -p 5144 > output.txt

-l will stop listening on connection closed (unlike -L)