refactor server tcp handling

- limit on number of tcp connections
- preliminary support for websockets

lib/rand_id.js

@@ -0,0 +1,12 @@
+
+var chars = 'abcdefghiklmnopqrstuvwxyz';
+module.exports = function rand_id() {
+    var randomstring = '';
+    for (var i=0; i<4; ++i) {
+        var rnum = Math.floor(Math.random() * chars.length);
+        randomstring += chars[rnum];
+    }
+
+    return randomstring;
+}
+