title: Why I can't listen 127.0.0.1:port by socket
body: <p>java.net.ConnectException: Connection refused (Connection refused)</p>
  
  <p>no program using the port</p>
  
  <pre class="lang-java prettyprint-override"><code>Socket socket = new Socket("127.0.0.1", 9876);
  </code></pre>
  
  <pre class="lang-java prettyprint-override"><code>java.net.ConnectException: Connection refused (Connection refused)
      at java.net.PlainSocketImpl.socketConnect(Native Method)
      at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
      at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
      at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
      at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
      at java.net.Socket.connect(Socket.java:589)
      at java.net.Socket.connect(Socket.java:538)
      at java.net.Socket.&lt;init&gt;(Socket.java:434)
      at java.net.Socket.&lt;init&gt;(Socket.java:211)
  </code></pre>