[Http] fiddler (1)-about fiddler

1. Why is it Fiddler?

There are many packet capture tools, ranging from the most commonly used Web debugging tool firebug to the powerful Generic Packet capture tool Wireshark. Why use Fiddler? The reason is as follows:

A. Although firebug can capture packets, it is not powerful enough to analyze the details of HTTP requests. The ability to simulate HTTP requests is not enough, and firebug often requires "refreshing new modifications". If the page is refreshed, all modifications will not be saved.

B. Wireshark is a common packet capture tool, but it is relatively large. For applications that only need to capture HTTP requests, it seems a little useless.

C. httpwatch is also a commonly used HTTP packet capture tool, but it only supports IE and Firefox browsers (other browsers may have corresponding plug-ins). If you want to debug Chrome HTTP, please, fiddler2 is an HTTP proxy that uses 127.0.0.1: 8888. You can use fiddler for any browser or application that can set the HTTP proxy to 127.0.0.1: 8888.

2. What is Fiddler?

Fiddler is an HTTP proxy on the client and server. It is also one of the most commonly used HTTP packet capture tools. It records all HTTP requests between the client and the server. It can analyze request data, set breakpoints, debug web applications, and modify request data for specific HTTP requests, it can even modify the data returned by the server. It has powerful functions and is a powerful tool for Web debugging.

Since it is a proxy, that is to say, all requests from the client must first pass through fiddler and then forward it to the corresponding server. Otherwise, all requests from the server will first pass through fiddler and then be sent to the client, for this reason, Fiddler supports all browsers and applications that can set the HTTP proxy to 127.0.0.1: 8888. After Fiddler is used, the Web client and server requests are as follows:

Fiddler acts as the system proxy. When Fiddler is enabled, the proxy setting of IE will change to 127.0.0.1: 8888. Therefore, if your browser does not set the corresponding proxy after Fiddler is enabled, then, Fiddler cannot capture HTTP requests. The proxy settings of IE browser are as follows:

 

Taking Firefox as an example, by default, Firefox does not enable proxy (if you have installed proxy and other proxy tools or plug-ins, it is another situation ), to configure an HTTP proxy in Firefox, follow these steps:

Tools> Options> advanced> network> Settings. Configure the corresponding proxy as follows:

You can use Fiddler to capture Firefox HTTP requests.

3. Introduction to the fiddler user interface

The layout of the fiddler main interface is as follows:

The main interface mainly includes four common blocks:

1. the menu bar of Fiddler, in green. These functions include capturing HTTP requests, stopping capture requests, saving HTTP requests, loading local sessions, and setting capture rules.

2. the toolbar of Fiddler, in red. This includes operations performed by Fiddler on the current view (pause, clear session, decode mode, clear cache, etc ).

3. the web session panel is in the yellow area. Each HTTP request captured by fiddler (called a session) contains the request URL, protocol, and status code, body and other information, detailed field meanings are shown in:

4. Details and Data Statistics Panel. Specific statistics on each HTTP Request (such as the number of bytes sent/received, the sending/receiving time, and the time spent on accessing the server around the world) and data packet analysis. For example, the Inspector Panel provides headers, textview, hexview, raw, and other methods to view the request message of a single HTTP request:

On the composer panel, you can simulate the process of sending data to the corresponding server (good, this is the basic principle of the irrigation robot, or part of the HTTP flood ).

You can also paste the raw HTTP headers of a request to simulate the request:

You can set a filter rule for Fiddler to filter HTTP requests. The simplest example is to filter Intranet HTTP requests and only capture Internet HTTP requests, or filter the HTTP requests of the corresponding domain name. The fiddler filter is very powerful. It can filter requests with specific HTTP status codes and filter HTTP requests of specific request types (such as CSS requests, image requests, and JS requests ), you can filter requests whose request packets are larger than or smaller than the specified size (byte:

More filter rules need to be mined step by step.

[Http] fiddler (1)-about fiddler