title: UnhandledPromiseRejectionWarning: MongoNetworkError: failed to connect to server [localhost:27017] on first connect [MongoNetworkError
body: <p>I tried to run the following command:</p>
  
  <pre><code>node index.js
  </code></pre>
  
  <p>However, I get the following from my terminal:</p>
  
  <pre><code>    success connection to port 3000
  (node:16767) UnhandledPromiseRejectionWarning: MongoNetworkError: failed to connect to server [localhost:27017] on first connect [MongoNetworkError
  : connect ECONNREFUSED 127.0.0.1:27017]
      at Pool.&lt;anonymous&gt; (/Users/hatchery/Documents/nodejs/fxexpress/node_modules/mongoose/node_modules/mongodb-core/lib/topologies/server.js:503:11
  )
      at emitOne (events.js:116:13)
      at Pool.emit (events.js:211:7)
      at Connection.&lt;anonymous&gt; (/Users/hatchery/Documents/nodejs/fxexpress/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:326:12)
      at Object.onceWrapper (events.js:317:30)
      at emitTwo (events.js:126:13)
      at Connection.emit (events.js:214:7)
      at Socket.&lt;anonymous&gt; (/Users/hatchery/Documents/nodejs/fxexpress/node_modules/mongoose/node_modules/mongodb-core/lib/connection/connection.js:245:50)
      at Object.onceWrapper (events.js:315:30)
      at emitOne (events.js:116:13)
      at Socket.emit (events.js:211:7)
      at emitErrorNT (internal/streams/destroy.js:64:8)
      at _combinedTickCallback (internal/process/next_tick.js:138:11)
      at process._tickCallback (internal/process/next_tick.js:180:9)
  (node:16767) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
  (node:16767) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
  </code></pre>
  
  <p>I am not sure why I am getting this error. Could anyone advice what to do?</p>