QuickIO is a very fast, very simple WebSocket server written entirely in C. Unlike other options, such as Socket.IO, that endeavor to be care-free, fun, and feature-rich, QIO is care-expensive, difficult, and not-too-featureful. The one advantage QIO has over all the others, though, is that it is fast. It's so fast even its name is fast.

In initial tests, running on a Large EC2 instance, QIO broke 1.5 million concurrent connections (from actual clients in the wild), used 450MB ram, and had a load average of .5. The server never even broke a sweat.

Originally, the project was called Q.IO, named after the omnipotent Q from Star Trek, implying that it gave your IO the power of Q. No one seemed to get the reference, so it just became easier to tell everyone it stood for "Quick".

• linux >= 2.6.30
• glib >= 2.32
• openssl >= 1.0.0
• tcmalloc >= 2.1
• doxygen + sphinx (for generating docs)

# For compiling
sudo aptitude install build-essential libglib2.0-dev libssl-dev libgoogle-perftools-dev

With check installed, run:

make test

If you're going to have a crap-ton (yes, that is a metric) of clients connected, you're going to need to tune some kernel parameters.

sudo sysctl -w fs.epoll.max_user_watches=4194304
sudo sysctl -w fs.file-max=4197304
sudo sysctl -w fs.nr_open=4197304
sudo sysctl -w net.core.somaxconn=1024
sudo sysctl -w net.ipv4.tcp_mem="2820736 3031648 3533472"
sudo sysctl -w net.netfilter.nf_conntrack_max=4194304

Most of the ideas are taken from: https://www.kernel.org/doc/Documentation/CodingStyle. As long as your code fits in, we're good.