Add support for binding to unix sockets

Fixes #686.
Fixes #691.

defaults/config.js

@@ -16,6 +16,8 @@ module.exports = {
 	// IP address or hostname for the web server to listen on.
 	// Setting this to undefined will listen on all interfaces.
 	//
+	// For UNIX domain sockets, use unix:/absolute/path/to/file.sock.
+	//
 	// @type     string
 	// @default  undefined
 	//

src/server.js

@@ -83,18 +83,30 @@ module.exports = function() {
 		}, app);
 	}
 
-	server.listen({
+	let listenParams;
+
+	if (typeof config.host === "string" && config.host.startsWith("unix:")) {
+		listenParams = config.host.replace(/^unix:/, "");
+	} else {
+		listenParams = {
 			port: config.port,
 			host: config.host,
-	}, () => {
+		};
+	}
+
+	server.listen(listenParams, () => {
+		if (typeof listenParams === "string") {
+			log.info("Available on socket " + colors.green(listenParams));
+		} else {
 			const protocol = config.https.enable ? "https" : "http";
-		var address = server.address();
+			const address = server.address();
 
 			log.info(
 				"Available at " +
 				colors.green(`${protocol}://${address.address}:${address.port}/`) +
 				` in ${colors.bold(config.public ? "public" : "private")} mode`
 			);
+		}
 
 		const sockets = io(server, {
 			serveClient: false,