chapter10

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Chapter 10
HTTP Servers

This is a directory of program listings from Chapter 10 of the book:

Foundations of Python Network Programming

Third Edition, October 2014
by Brandon Rhodes and John Goerzen

You can learn more about the book by visiting the root of this GitHub source code repository.

These scripts were written for Python 3, but can also run successfully under Python 2. Simply use 3to2 to convert them to the older syntax. Then edit wsgi_env.py to remove the u in front of its string literals, because wsgiref cannot process Unicode headers or status codes (whereas gunicorn, with which we run the other example servers, does not seem to have a problem).

The wsgi_env.py script is designed to familiarize the reader with what a live WSGI environment dictionary looks like. When contacted, it replies with a pretty-printed version of the dictionary:

$ python3 wsgi_env.py &
Serving on 0.0.0.0 port 8000

$ curl -s http://127.0.0.1:8000/ && echo
127.0.0.1 - - [25/Mar/2014 19:20:08] "GET / HTTP/1.1" 200 3517
Here is the WSGI environment:

{'BASH_ENV': '$HOME/.bashenv',
 'CONDA_DEFAULT_ENV': '/home/brandon/.v/fopnp-py3',
 'CONTENT_LENGTH': '',
 'CONTENT_TYPE': 'text/plain',
 'DBUS_SESSION_BUS_ADDRESS': 'unix:abstract=/tmp/dbus-jbCOBCOyCX',
 'DEFAULTS_PATH': '/usr/share/gconf/xfce.default.path',
 'DESKTOP_SESSION': 'xfce',
 'DISPLAY': ':0.0',
 'EDITOR': '/home/brandon/bin/enw',
 'FVWM_MODULEDIR': '/usr/lib/fvwm/2.6.5',
 'FVWM_USERDIR': '/home/brandon/.fvwm',
 'GATEWAY_INTERFACE': 'CGI/1.1',
 'GDMSESSION': 'xfce',
 'GDM_LANG': 'en_US',
 'GLADE_CATALOG_PATH': ':',
 'GLADE_MODULE_PATH': ':',
 'GLADE_PIXMAP_PATH': ':',
 'GNOME_KEYRING_CONTROL': '/run/user/1000/keyring-oSpEEj',
 'GNOME_KEYRING_PID': '1816',
 'GREP_COLOR': '1;32',
 'GREP_OPTIONS': '--color=auto',
 'HOME': '/home/brandon',
 'HOSTDISPLAY': 'guinness:0.0',
 'HTTP_ACCEPT': '*/*',
 'HTTP_HOST': '127.0.0.1:8000',
 'HTTP_USER_AGENT': 'curl/7.35.0',
 'IM_CONFIG_PHASE': '1',
 'INSTANCE': '',
 'JOB': 'dbus',
 'LANG': 'C.UTF-8',
 'LANGUAGE': 'en_US',
 'LC_COLLATE': 'C',
 'LC_CTYPE': 'en_US.UTF-8',
 'LESS': '-i -j.49 -M -R -z-2',
 'LOGNAME': 'brandon',
 'LSCOLORS': 'Gxfxcxdxbxegedabagacad',
 'MANDATORY_PATH': '/usr/share/gconf/xfce.mandatory.path',
 'OLDPWD': '/home/brandon/fopnp/py3',
 'PAGER': 'less',
 'PATH': '/home/brandon/.v/fopnp-py3/bin:/home/brandon/bin:/home/brandon/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games',
 'PATH_INFO': '/',
 'PIP_DOWNLOAD_CACHE': '/home/brandon/.cache/pip',
 'PWD': '/home/brandon/fopnp/py3/chapter10',
 'PYTHONDONTWRITEBYTECODE': 'PLEASE',
 'PYTHONPATH': '/home/brandon/fopnp/py3/tools/monkeys',
 'QUERY_STRING': '',
 'REMOTE_ADDR': '127.0.0.1',
 'REMOTE_HOST': '',
 'REQUEST_METHOD': 'GET',
 'SCRIPT_NAME': '',
 'SELINUX_INIT': 'YES',
 'SERVER_NAME': 'guinness',
 'SERVER_PORT': '8000',
 'SERVER_PROTOCOL': 'HTTP/1.1',
 'SERVER_SOFTWARE': 'WSGIServer/0.2',
 'SESSION': 'xfce',
 'SESSIONTYPE': '',
 'SESSION_MANAGER': 'local/guinness:@/tmp/.ICE-unix/1959,unix/guinness:/tmp/.ICE-unix/1959',
 'SHELL': '/bin/zsh',
 'SHLVL': '2',
 'SSH_AGENT_LAUNCHER': 'upstart',
 'SSH_AGENT_PID': '1910',
 'SSH_AUTH_SOCK': '/tmp/ssh-DW8Gpm8QY5aS/agent.1908',
 'TERM': 'xterm',
 'TEXTDOMAIN': 'im-config',
 'TEXTDOMAINDIR': '/usr/share/locale/',
 'UPSTART_EVENTS': 'started xsession',
 'UPSTART_INSTANCE': '',
 'UPSTART_JOB': 'startxfce4',
 'UPSTART_SESSION': 'unix:abstract=/com/ubuntu/upstart-session/1000/1828',
 'USER': 'brandon',
 'WINDOWID': '83886114',
 'XAUTHORITY': '/home/brandon/.Xauthority',
 'XDG_CONFIG_DIRS': '/etc/xdg/xdg-xfce:/usr/share/upstart/xdg:/etc/xdg:/etc/xdg',
 'XDG_CURRENT_DESKTOP': 'XFCE',
 'XDG_DATA_DIRS': '/usr/share/xfce:/usr/share/xfce4:/usr/local/share/:/usr/share/:/usr/share',
 'XDG_GREETER_DATA_DIR': '/var/lib/lightdm-data/brandon',
 'XDG_MENU_PREFIX': 'xfce-',
 'XDG_RUNTIME_DIR': '/run/user/1000',
 'XDG_SEAT': 'seat0',
 'XDG_SEAT_PATH': '/org/freedesktop/DisplayManager/Seat0',
 'XDG_SESSION_ID': 'c2',
 'XDG_SESSION_PATH': '/org/freedesktop/DisplayManager/Session0',
 'XDG_VTNR': '7',
 'XTERM_LOCALE': 'en_US.UTF-8',
 'XTERM_SHELL': '/bin/zsh',
 'XTERM_VERSION': 'XTerm(297)',
 '_': '/home/brandon/.v/fopnp-py3/bin/python3',
 'wsgi.errors': <_io.TextIOWrapper name='<stderr>' mode='w' encoding='UTF-8'>,
 'wsgi.file_wrapper': <class 'wsgiref.util.FileWrapper'>,
 'wsgi.input': <_io.BufferedReader name=5>,
 'wsgi.multiprocess': False,
 'wsgi.multithread': True,
 'wsgi.run_once': False,
 'wsgi.url_scheme': 'http',
 'wsgi.version': (1, 0)}

Note that the && echo command that has been appended to curl in all of these shell command lines is simply there to provide a newline before your shell prompt displays again, because none of these HTTP responses include a trailing newline.

The other three scripts in this chapter implement the same tiny WSGI network service. One speaks “raw WSGI” per the PEP, while the other two use third-party libraries that wrap WSGI in pretty request and response objects.

$ gunicorn -b ':8001' timeapp_raw:app &

$ gunicorn -b ':8002' timeapp_werkz:app &

$ gunicorn -b ':8003' timeapp_webob:app &

$ curl -s http://127.0.0.1:8001/ && echo
Wed Oct 22 15:55:54 2014

$ curl -s http://127.0.0.1:8002/ && echo
Wed Oct 22 15:55:55 2014

$ curl -s http://127.0.0.1:8003/ && echo
Wed Oct 22 15:55:56 2014

The sample network service simply returns the current time.