The intersection of technology and leadership

Ruby Script to Capture HTTP traffic

I spent some time early this week trying to debug why some test was failing. It was using RESTeasy and I wanted to find out exactly what HTTP packets it was sending. If I was on a windows machine, I’d look towards Fiddler, but I couldn’t find anything easy on mac, so I wrote a little ruby script that I could point the client at and dump out all headers and request body.

It looks like this:

require 'webrick'
include WEBrick

class Simple < WEBrick::HTTPServlet::AbstractServlet
  def do_POST(request, response)
    puts "Body: " + request.body
    puts "Header: " + request.raw_header.to_s

    response.status = 200

server = => 5899)
server.mount "/", Simple

['TERM', 'INT'].each do |signal|
trap(signal){ server.shutdown }


Upon publishing this, I got a couple of alternatives worth looking into for next time.

  • Jim suggested using tcptrace; and
  • Gaz suggested using the following command sudo tcpdump -vvv -A -s 0 -i en1 tcp ‘port 5899’

This is just yet another example about why it’s important to have diversity when problem solving. I didn’t even know about these tools. Now I do and you do too.


  1. Hey Pat,

    Why not just use tcptrace?


  2. @Jim because then poor Pat doesn’t get to code at all 😉

  3. That’s because I didn’t know about it. Now I do. I’m guessing that this is the one you’re talking about?

  4. Markus Krogemann

    July 3, 2011 at 2:46 pm

    maybe the tcpmon.jar (somewhere at apache) could have helped you here? I’ve used it a lot to reverse engineer undocumented http traffic 🙂

  5. Chris McGrath

    July 4, 2011 at 12:30 am

    For general browser sniffing have a look at Charles Proxy too. It’s saved me *way* more money than it cost over the years.

  6. Hi Markus,

    I didn’t know about this one either. Looks good. I’ll give it a go next time.

  7. Hi Chris,

    I had a look at Charles proxy but it was a bit fiddly to set up. I’ll have to bookmark that one now too. Thanks!

  8. Checkout paros and burp proxy, they r cool as well

  9. Thanks. I’ll have to take a look at them too

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