July 2, 2011

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
  end
end

server = HTTPServer.new(:Port => 5899)
server.mount "/", Simple

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

server.start

Update
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.