client refers to irc.Client() created with node-irc socket is socket.io instance generated by "connection" event. Not really needed so you an take them out if you don't need sockets.
add this line to your package.json: { ... "piped-xdcc": "penandlim/piped-xdcc" }
Dependencies I used:
"dependencies": {
"ejs": "2.5.6",
"express": "4.15.2",
"irc": "martynsmith/node-irc",
"mime-types": "^2.1.17",
"piped-xdcc": "penandlim/piped-xdcc",
"socket.io": "^2.0.3"
},