Serve text file via HTTP protocol using netcat

Unix based system provide a lot of cool network tools, today I'd like to show the potential of netcat. Netcat is a utility that may be used for "just about anything under the sun involving TCP and UDP" (netcat BSD manual) . Thats a pretty description, but let's go on to some practical stuff.

If we want to make a useful script, we should make it work with a popular protocol, such as HTTP. This way we don't have to worry about potential client application, we may use an ordinary web browser to test our script. More formal information about the HTTP protocol can be found in RFC2616.

So a bash script that generates a simple HTTP response and serves a text file may look like this:

if [ -z "$1" ]
then
    echo "Usage: $0 <text file to serve>"
    exit 1
fi

filename=$1

echo "
HTTP/1.1 200 OK
Date: $(LANG=en_US date -u) 
Server: NetCatFileServe
Last-Modified: $(LANG=en_US date -u)
Accept-Ranges: bytes
Content-Length: $(cat $filename | wc -c  | cut -d " " -f 1) 
Content-Type: application/force-download
Content-Disposition: attachment; filename=\"$filename\"

$(cat $filename)
"

If a HTTP client receives such a response, it should try to save the attached data as a file (a typical save-file-as window in a web browser).

Since we have a HTTP response generate, we need to create a server that will serve it - that's where netcat comes in handy. To serve some data we need to run it in the listening mode. For example :

~ $ ./ncserve.sh test.txt | nc -l 8888

If you now enter http://127.0.0.1:8888 (or your other IP) in a webbrowser, you should be able to download text.txt  file. You may also  test it using curl:

~ $ curl -X GET 127.0.0.1:8888
HTTP/1.1 200 OK
Date: Sat Oct 13 10:40:27 UTC 2012
Server: NetCatFileServe
Last-Modified: Sat Oct 13 10:40:27 UTC 2012
Accept-Ranges: bytes
Content-Length: 71
Content-Type: application/force-download
Content-Disposition: attachment; filename="test.txt"

This is a simple text file
bla bla bla
downloaded via netcatserver
:-)

This script only serve a file once and dies, if you want it to act like a regular HTTP server you should run it in a infinite loop.

Cheers!

~KR