server-sent events (#177)

* server-sent events

* remove stale clients

* ping as message

server-sent-events/drain.js

@@ -0,0 +1,36 @@
+const http = require('http')
+
+let drop_goal = 10_000;
+let dropped = 0;
+
+let query = {
+    host: 'localhost',
+    port: 8080,
+    path: '/events'
+}
+
+setInterval(() => {
+    if (dropped < drop_goal) {
+        let request = http.get(query, response => {
+            response.on('data', data => {
+                if (data.includes("data: connected\n")) {
+                    // drop connection after welcome message
+                    dropped += 1;
+                    request.abort()
+                }
+            })
+        })
+        .on('error', () => {})
+    }
+}, 1)
+
+setInterval(() => {
+    http.get('http://localhost:8080/', () => print_status(true))
+        .setTimeout(100, () => print_status(false))
+        .on('error', () => {})
+}, 20)
+
+function print_status(accepting_connections) {
+    process.stdout.write("\r\x1b[K");
+    process.stdout.write(`Connections dropped: ${dropped}, accepting connections: ${accepting_connections}`);
+}