Merge pull request #8127 from nightscout/wip/bewest/restore-v2

socket.io: enable legacy v2 connections

Author: bewest

lib/server/websocket.js

@@ -75,7 +75,9 @@ function init (env, ctx, server) {
       'log level': 0
     }).listen(server, {
       //these only effect the socket.io.js file that is sent to the client, but better than nothing
-      'browser client minification': true
+      // compat with v2 client
+      allowEIO3: true
+      , 'browser client minification': true
       , 'browser client etag': true
       , 'browser client gzip': false
       , 'perMessageDeflate': {