Bash – Can’t pipe echo to netcat

bashechomacnetcatpipe

I have the following command:

echo 'HTTP/1.1 200 OK\r\n' | nc -l -p 8000 -c

and when I curl localhost:8000 I am not seeing HTTP/1.1 200 .. being printed.

I am on mac os x with netcat 0.7.1

Any ideas? 

#!/bin/bash

trap 'my_exit; exit' SIGINT SIGQUIT

my_exit()
{
        echo "you hit Ctrl-C/Ctrl-\, now exiting.."
        # cleanup commands here if any
}

if test $# -eq 0 ; then
        echo "Usage: $0 PORT"
        echo ""
        exit 1
fi

while true
do
        echo "HTTP/1.1 200 OK\r\n" | nc -l -p ${1} -c
done

and testing with:

curl localhost:8000

Best Answer

Your approach has multiple issues.

Escape sequences

The escape sequences are not honored unless you use the -e switch.

echo -e 'HTTP/1.1 200 OK\r\n'

Without -e, you are sending the backslashes and letters verbatim. The above forms a full HTTP status line.

Protocol

The status line alone does not constitute a response. The format requires two CRLFs

  1. One as part of the Status Line itself
  2. One to terminate the respnse header

Try this

echo -e 'HTTP/1.1 200 OK\r\n\r\n'

netcat invocation

The -c flag is plain wrong, because it expects a command argument.

echo -e 'HTTP/1.1 200 OK\r\n\r\n' | nc -l -p $port

Content

Even with that, curl will block after receiving the reply, because it's waiting for the server to supply a body. You could either send more data to nc, or choose a more appropriate answer.

echo -e 'HTTP/1.1 204 No content\r\n\r\n' | nc -l -p $port

Note that curl will print just what it receives - nothing. Try curl -v to get a glimpse of what's going on.

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