check the server parameter

capaj · Aug 23, 2016 · 7b3f78d · 7b3f78d
1 parent ba4cac9
commit 7b3f78d
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/index.js b/index.js
@@ -68,6 +68,9 @@ const gatherOsMetrics = (io, span) => {
 const encoding = {encoding: 'utf8'}
 
 const middlewareWrapper = (app, config) => {
+  if (!app.listen) {
+    throw new Error('First parameter must be an http server')
+  }
   io = require('socket.io')(app)
   Object.assign(defaultConfig, config)
   config = defaultConfig