##master-page:HomepageReadWritePageTemplate
##master-date:Unknown-Date
#format wiki
#language en
= Websockets =
 * 2013 - New way for javascript to open a tcp connection back to the server for data transfer.

 * Here is some notes as I struggled to get the first examples to work.

  * Errors in apache log files
    1. {{{ Exception: ('PythonOption mod_pywebsocket.handler_root is not defined', 3)  }}}
    1. {{{ AttributeError: object has no attribute  "APLOG_DEBUG" }}}
 
  * Cause was that i had to have the websocket config above the default virtual server in my apache2 config file.
 {{{
##PES 2013 pywebsocket
<IfModule python_module>
  PythonPath "sys.path+['/mod_pywebsocket']"
  PythonOption mod_pywebsocket.handler_root /var/www
  PythonOption mod_pywebsocket.handler_scan /var/www/ws
  #PythonOption mod_pywebsocket.allow_draft75 On
  <Location /ws>
    PythonHeaderParserHandler mod_pywebsocket.headerparserhandler
  </Location>
</IfModule>  

<VirtualHost *:80>

	ServerAdmin webmaster@localhost

	DocumentRoot /var/www
	<Directory />
		Options FollowSymLinks
		AllowOverride None
	</Directory>
	<Directory /var/www/>
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	</Directory>
	ErrorLog ${APACHE_LOG_DIR}/error.log
        LogLevel debug
	CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
}}}

 * To test
   1. copy file '''echo_wsh.py''' into /var/www/ws
   2. open webpage to test '''file:///usr/share/doc/python-mod-pywebsocket/examples/console.html''' in browser
   3. test by entering in webpage abe the url  '''ws://localhost/ws/echo'''
   4. on web page in display window you should see message '''Connect ws://localhost/ws/echo'''


 * Another problem was with /var/www/ws/websockify_wsh.py
   * Found in Apache2 log  '''websockify: ws_protocol = 'binary' (['binary', 'base64'])'''
   * It was picking binary for socket and noVNC only supports base64.
     * Solution, just before it picked the first option, i check for base64 and rather select it.
 
 * Another problem, connecting with vnc.html, found in apache2 log.
   {{{mod_pywebsocket: websockify: connection denied: 'NoneType' object has no attribute 'split'}}}

...
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CategoryDevelopement