So, if you decide to use socket.io in one of your projects, you might come accross the following error:

ERROR [karma]: [Error: error:24064064:random number generator:SSLEAY_RAND_BYTES:PRNG not seeded]

followed by a long and scary stack traceback. Not to worry there's a fix for that!

Open the file:

node_modules/karma/node_modules/socket.io/lib/manager.js

Go to line 734 (it might actually be a couple of lines above or below that, look around!) and replace the following snippet:

if (crypto.randomBytes) {
    crypto.randomBytes(12).copy(rand);
} else { ....

with this:

if (crypto.pseudoRandomBytes) {
    crypto.pseudoRandomBytes(12).copy(rand);
} else {

That's it! It should be good to go now!