Question

In previous jobs when I've worked on a Windows machine, I've used Fiddler for viewing HTTP transactions and debugging.

I'm specifically looking to monitor the HTTP transactions for an ajax site I'm working on to verify that the site is doing what I expect. Rewriting HTTP (as provided by Fiddler) is a nice-to-have, but not essential.

Can anybody recommend something similar for use on a Mac?

Answer 1

Not what you asked, but in Firefox the Live HTTP Headers add-on is all I need if I want to edit and re-play requests.

In Firebug, the Network Monitoring shows all requests and responses. Likewise, in Safari the Resources pane of the built-in Web Inspector covers most of my needs as well, but does not show the payload of POST Ajax/XHR requests (the responses are fine though). The latter has been fixed in the source code on August 31 2009, and some day will be updated in a new version of Safari. It might also apply to other browsers that use WebKit's inspector, such as Google Chrome. (Enable the Web Inspector through the preferences: Show Develop menu in menu bar.)

When things get more complicated, I fire up my Wireshark packet sniffer. However, unlike Fiddler, Wireshark does not let you change the data, and does not support things like auto responders, like Fiddler apparently does.

For Wireshark, see Hyper Text Transfer Protocol (HTTP) for some generic HTTP capturing information, and HTTP Packet Capturing to debug Apache, for some example display filters. (You may want to set the capture filter to "port 80", to show all requests to that port, and responses from that port. Or, to limit to some server, use capture filter "port 80 and host www.google.com".) Like:

# Show only 404: page not found
http.response.code == 404

# Show only certain HTTP methods
http.request.method == "POST" || http.request.method == "PUT"

# Show only javascript
http.content_type contains "javascript"

Note that Wireshark can decompress gzip or deflate encoded (compressed) things on the fly for you. That makes things much easier to read as most web servers will compress the data they send to a browser.

(As for auto responders: the excellent JS Bin has a short video on how to use it to debug Ajax requests. If you don't know JS Bin, then first view the introduction video.)

Answer 2

My favorite mac app for monitoring traffic is HTTPScoop, I detail that as well as using tcpdump from the commandline in this post I blogged last year.

Answer 3

I found Charles Proxy. It's much closer to the functionality of Fiddler. It's not free, but it may be worth the price.

Answer 4

I'm late but - I use Paros Proxy. It's in Java, so, cross-platform. Though if you would prefer for it to be packaged as an app, there's one here at the bottom.

Answer 5

It seems that the free GlimmerBlocker can do part of the trick.

Of course it can block all kind of content, and transform responses before the browser receives them. But it can in fact modify both requests and responses. And though not true debugging, it also offers logging. So, it might suit basic needs:

There are 4 types of scripts running inside GlimmerBlocker, and some objects are only defined for some of the script types:

• global proxy: this sets the global proxy settings, and can test for e.g. location name, AirPort network.
• request modification: this can change the requested URL, send back a redirect response to the browser, or send text/html back to the browser.
• keyword expansion. [Safari-only, AvB]
• transform: modify the response received by the web-server before it is sent back to Safari [or any browser that is set up to use the proxy provided by GlimmerBlocker, AvB].

(One can also use it to include various Greasemonkey scripts in the received response, without using a Greasemonkey add-on, like to block Flash without installing any add-on.)