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httpcat is a simple utility for constructing raw HTTPrequests on the command line.

Sometimes it is useful to be able to create an actual rawHTTP requeston 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 ashttpie,curl,orwget—are too high-level as they providean abstraction layer and one doesn't have a complete control over theexact raw data that gets written to the HTTP socket connection.

Lower-level tools, such as the popularnetcat, are better suited for thisjob.

However, the syntax of HTTP requires headers to be separated with\r\n which 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

httpcat makes this easier:

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

• Automatic\r\n completion
• AutomaticMethod completion inRequest-Line
• AutomaticHTTP-Version completion inRequest-Line

Interactively create a request and send it withnc:

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

Specify the whole request in the arguments. Here'' represents an emptyline which will be converted to\r\n\ separating the headers and thebody. Note also that the omittedHTTP-Version is 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

OmittedMethod is set toGET andHTTP-Version is 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, usestdin for 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 stdinoptional 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

• Python 3

pip3 install httpcat

Alternatively, you can just downloadhttpcat.py manually and invokeit as./httpcat.py instead ofhttpcat.

python3 setup.pytest

HTTPie CLI starting with version 2.0.0 also provides an--offline mode. This makes it a good alternative tohttpcat because 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/1.1Accept: application/json, */*;q=0.5Accept-Encoding: gzip, deflateConnection: keep-aliveContent-Length: 5Content-Type: application/jsonHost: httpbin.orgUser-Agent: HTTPie/2.2.0Hello

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

• 0.0.2 (2016-12-13)

  • Added-v, --verbose and 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.

Jakub Roztocil

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