httpcat

httpcatis a simple utility for constructing raw HTTP requests on the command line.

Why?

Sometimes it is useful to be able to create an actual raw HTTP request on the command line:

• To debug a server issue
• To test the handling of invalid HTTP requests
• To learn how HTTP works under the hood

In such cases, existing CLI HTTP clients—such as httpie, curl, orwget —are too high-level as they provide an abstraction layer and one doesn't have a complete control over the exact raw data that gets written to the HTTP socket connection.

Lower-level tools, such as the popular netcat,are better suited for this job.

However, the syntax of HTTP requires headers to be separated with \r\nwhich makes it difficult to produce them on the command line. A typical solution involves the use ofecho:

$echo-ne'POST /post HTTP/1.1\r\nHost: httpbin.org\r\nContent-Length: 5\r\n\r\nHello'|\
nc localhost 8000

httpcatmakes this easier:

How it works

1. Reads command arguments as lines and then lines fromstdin
2. Auto-completes them, if necessary
3. Writes them tostdout

Features

• Automatic\r\ncompletion
• AutomaticMethodcompletion inRequest-Line
• AutomaticHTTP-Versioncompletion inRequest-Line

Usage

Interactively create a request and send it withnc:

$ httpcat -v|nc httpbin.org 80
POST /post HTTP/1.1
>POST /post HTTP/1.1\r\n
Host: httpbin.org
>Host: httpbin.org\r\n
Content-Length: 6
>Content-Length: 6\r\n

>\r\n
Hello
>Hello

Specify the whole request in the arguments. Here''represents an empty line which will be converted to\r\n\separating the headers and the body. Note also that the omittedHTTP-Versionis auto-completed:

$ httpcat -v'POST /post''Host: httpbin.org''Content-Length: 5''''Hello'|nc httpbin.org 80
>POST /post HTTP/1.1\r\n
>Host: httpbin.org\r\n
>Content-Length: 5\r\n
>\r\n
>Hello

OmittedMethodis set toGETandHTTP-Versionis auto-completed:

$ httpcat -v /'Host: example.org'''|nc example.org 80
>GET / HTTP/1.1\r\n
>Host: example.org\r\n
>\r\n

You can, for example, usestdinfor data and arguments for headers:

$ cat file.txt|httpcat -v'POST /post''Host: httpbin.org''Content-Length: 16'''|nc httpbin.org 80
>POST /post HTTP/1.1\r\n
>Host: httpbin.org\r\n
>Content-Length: 16\r\n
>\r\n
>Hello from file

See alsohttpcat --help:

usage: httpcat [-h] [-V, --version] [-v] [-n] [line [line...]]

Create raw HTTP requests on the command line.

positional arguments:
line input lines read before lines from stdin

optional arguments:
-h, --help show this help message and exit
-V, --version show program's version number and exit
-v, --verbose print info about output lines to stderr
-n, --no-stdin disable reading of lines from stdin

Dependencies

• Python 3

Installation

pip3 install httpcat

Alternatively, you can just downloadhttpcat.pymanually and invoke it as./httpcat.pyinstead ofhttpcat.

Tests

Python 3 setup.pytest

HTTPie offline mode

HTTPie CLIstarting with version 2.0.0 also provides an--offlinemode.This makes it a good alternative tohttpcatbecause it provides a convenient mechanism for crafting arbitrary HTTP requests without sending them using the user-friendly HTTPie syntax, for example:

echo-n'Hello'|http --offline POST httpbin.org/post

The above command generates the following output:

POST/post HTTP/1.1
Accept:application/json, */*;q=0.5
Accept-Encoding:gzip, deflate
Connection:keep-alive
Content-Length:5
Content-Type:application/json
Host:httpbin.org
User-Agent:HTTPie/2.2.0

Hello

The output is valid HTTP, so it can simply be sent usingnc:

$echo-n'Hello'|http --offline POST httpbin.org/post|nc httpbin.org 80

Changelog

• 0.0.2(2016-12-13)

  • Added-v, --verboseand the command is more quiet by default.
  • Added-n, --no-stdin
  • Added-h, --help
  • Added-V, --version

• 0.0.1(2016-12-12)

  • Initial release.

Contact

Jakub Roztocil

• https://github /jkbrzt
• https://twitter /jkbrzt
• http://roztocil.co