Add WebSocket test client and server code.

server.js

@@ -0,0 +1,14 @@
+const http = require('http')
+const WebSocket = require('ws')
+
+const server = http.createServer()
+const wss = new WebSocket.Server({ server })
+
+wss.on('connection', ws => {
+  ws.on('message', msg => {
+    ws.send(`echo ${msg}`)
+    console.log(`Received: ${msg}`)
+  })
+})
+
+server.listen(8078)