title: Jupyter notebook: The port is already in use, trying another port?
body: <p>I can join the port sucessfully by 
  <code>ssh -N -L 8888:127.0.0.1:8888 server_ip</code></p>
  
  <p>But if I just join the server, and then use <code>jupyter notebook</code>, I can't open the port sucessfully.</p>
  
  <pre><code>ssh server_ip
  jupyter notebook --port=8888
  </code></pre>
  
  <p><code>Error:</code></p>
  
  <pre><code>The port 8888 is already in use, trying another port.
  </code></pre>
  
  <p>What is the reason and how to solve it?</p>