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29
30
31"""WebSocket extension for Apache HTTP Server.
32
33mod_pywebsocket is a WebSocket extension for Apache HTTP Server
34intended for testing or experimental purposes. mod_python is required.
35
36
37Installation:
38
390. Prepare an Apache HTTP Server for which mod_python is enabled.
40
411. Specify the following Apache HTTP Server directives to suit your
42   configuration.
43
44   If mod_pywebsocket is not in the Python path, specify the following.
45   <websock_lib> is the directory where mod_pywebsocket is installed.
46
47       PythonPath "sys.path+['<websock_lib>']"
48
49   Always specify the following. <websock_handlers> is the directory where
50   user-written WebSocket handlers are placed.
51
52       PythonOption mod_pywebsocket.handler_root <websock_handlers>
53       PythonHeaderParserHandler mod_pywebsocket.headerparserhandler
54
55   To limit the search for WebSocket handlers to a directory <scan_dir>
56   under <websock_handlers>, configure as follows:
57
58       PythonOption mod_pywebsocket.handler_scan <scan_dir>
59
60   <scan_dir> is useful in saving scan time when <websock_handlers>
61   contains many non-WebSocket handler files.
62
63   If you want to support old handshake based on
64   draft-hixie-thewebsocketprotocol-75:
65
66       PythonOption mod_pywebsocket.allow_draft75 On
67
68   If you want to allow handlers whose canonical path is not under the root
69   directory (i.e. symbolic link is in root directory but its target is not),
70   configure as follows:
71
72       PythonOption mod_pywebsocket.allow_handlers_outside_root_dir On
73
74   Example snippet of httpd.conf:
75   (mod_pywebsocket is in /websock_lib, WebSocket handlers are in
76   /websock_handlers, port is 80 for ws, 443 for wss.)
77
78       <IfModule python_module>
79         PythonPath "sys.path+['/websock_lib']"
80         PythonOption mod_pywebsocket.handler_root /websock_handlers
81         PythonHeaderParserHandler mod_pywebsocket.headerparserhandler
82       </IfModule>
83
842. Tune Apache parameters for serving WebSocket. We'd like to note that at
85   least TimeOut directive from core features and RequestReadTimeout
86   directive from mod_reqtimeout should be modified not to kill connections
87   in only a few seconds of idle time.
88
893. Verify installation. You can use example/console.html to poke the server.
90
91
92Writing WebSocket handlers:
93
94When a WebSocket request comes in, the resource name
95specified in the handshake is considered as if it is a file path under
96<websock_handlers> and the handler defined in
97<websock_handlers>/<resource_name>_wsh.py is invoked.
98
99For example, if the resource name is /example/chat, the handler defined in
100<websock_handlers>/example/chat_wsh.py is invoked.
101
102A WebSocket handler is composed of the following three functions:
103
104    web_socket_do_extra_handshake(request)
105    web_socket_transfer_data(request)
106    web_socket_passive_closing_handshake(request)
107
108where:
109    request: mod_python request.
110
111web_socket_do_extra_handshake is called during the handshake after the
112headers are successfully parsed and WebSocket properties (ws_location,
113ws_origin, and ws_resource) are added to request. A handler
114can reject the request by raising an exception.
115
116A request object has the following properties that you can use during the
117extra handshake (web_socket_do_extra_handshake):
118- ws_resource
119- ws_origin
120- ws_version
121- ws_location (Hixie 75 and HyBi 00 only)
122- ws_extensions (Hybi 06 and later)
123- ws_deflate (HyBi 06 and later)
124- ws_protocol
125- ws_requested_protocols (HyBi 06 and later)
126
127The last two are a bit tricky.
128
129For HyBi 06 and later, ws_protocol is always set to None when
130web_socket_do_extra_handshake is called. If ws_requested_protocols is not
131None, you must choose one subprotocol from this list and set it to
132ws_protocol.
133
134For Hixie 75 and HyBi 00, when web_socket_do_extra_handshake is called,
135ws_protocol is set to the value given by the client in
136Sec-WebSocket-Protocol (WebSocket-Protocol for Hixie 75) header or None if
137such header was not found in the opening handshake request. Finish extra
138handshake with ws_protocol untouched to accept the request subprotocol.
139Then, Sec-WebSocket-Protocol (or WebSocket-Protocol) header will be sent to
140the client in response with the same value as requested. Raise an exception
141in web_socket_do_extra_handshake to reject the requested subprotocol.
142
143web_socket_transfer_data is called after the handshake completed
144successfully. A handler can receive/send messages from/to the client
145using request. mod_pywebsocket.msgutil module provides utilities
146for data transfer.
147
148You can receive a message by the following statement.
149
150    message = request.ws_stream.receive_message()
151
152This call blocks until any complete text frame arrives, and the payload data
153of the incoming frame will be stored into message. When you're using IETF
154HyBi 00 or later protocol, receive_message() will return None on receiving
155client-initiated closing handshake. When any error occurs, receive_message()
156will raise some exception.
157
158You can send a message by the following statement.
159
160    request.ws_stream.send_message(message)
161
162Executing the following statement or just return-ing from
163web_socket_transfer_data cause connection close.
164
165    request.ws_stream.close_connection()
166
167When you're using IETF HyBi 00 or later protocol, close_connection will wait
168for closing handshake acknowledgement coming from the client. When it
169couldn't receive a valid acknowledgement, raises an exception.
170
171web_socket_passive_closing_handshake is called after the server receives
172incoming closing frame from the client peer immediately. You can specify
173code and reason by return values. They are sent as a outgoing closing frame
174from the server. A request object has the following properties that you can
175use in web_socket_passive_closing_handshake.
176- ws_close_code
177- ws_close_reason
178
179A WebSocket handler must be thread-safe if the server (Apache or
180standalone.py) is configured to use threads.
181"""
182
183
184# vi:sts=4 sw=4 et tw=72
185