Configuring Apache2 to proxy WebSocket

apache-2.2PROXYwebsocket

The WebSocket protocol is an extension of the HTTP protocol. However, the proxy module of Apache2 does not seem to know about it, and throws away crucial headers, converting the call to a standard HTTP call.

Is there a way to make Apache2 either (1) understand WebSocket or (2) simply blindly pass on whatever it gets?

Best Answer

There is now a module in the Apache trunk called mod_proxy_wstunnel which allows mod_proxy (ProxyPass/ProxyPassReverse) to pass through WebSocket traffic. Someone wrote a blog post about back-porting mod_proxy_wstunnel to Apache 2.4/2.2 and provided a patch to do so.

I figured out concrete instructions to set up mod_proxy_wstunnel on Ubuntu (tested with Ubuntu Server 11.10 and Apache 2.2.20) and posted them on my blog. I have copied them below:

# Check apache version (should be 2.2.20 as of writing, if not adjust the next step)
dpkg -s apache2

# Checkout apache source
svn checkout http://svn.apache.org/repos/asf/httpd/httpd/tags/2.2.20/ httpd-2.2.20

# Get patch and apply it
wget http://cafarelli.fr/gentoo/apache-2.2.24-wstunnel.patch
cd httpd-2.2.20
patch -p1 < ../apache-2.2.24-wstunnel.patch

# Build Apache 
svn co http://svn.apache.org/repos/asf/apr/apr/branches/1.4.x srclib/apr
svn co http://svn.apache.org/repos/asf/apr/apr-util/branches/1.3.x srclib/apr-util
./buildconf
./configure --enable-proxy=shared --enable-proxy_wstunnel=shared
make

# Copy the module and recompiled mod_proxy (for new symbols) to the ubuntu apache installation and update the permissions to match the other modules
sudo cp modules/proxy/.libs/mod_proxy{_wstunnel,}.so /usr/lib/apache2/modules/
sudo chmod 644 /usr/lib/apache2/modules/mod_proxy{_wstunnel,}.so
echo -e "# Depends: proxy\nLoadModule proxy_wstunnel_module /usr/lib/apache2/modules/mod_proxy_wstunnel.so" | sudo tee -a /etc/apache2/mods-available/proxy_wstunnel.load

# Enable the module (also make any configuration changes you need)
sudo a2enmod proxy_wstunnel
sudo service apache2 restart
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