title: Network traffic through a particular port using iftop
body: <p>I have a process using https. I found its PID using <code>ps</code> and used the command <code>lsof -Pan -p PID -i</code> to get the port number it is running on. </p>
  
  <p>I need iftop to see the data transfer. The filter I am using now is 
  <code>iftop -f "port http 57787"</code>. </p>
  
  <p>I don't think this is giving me the right output. 
  Can someone help me the right filter to use with iftop so that I know the traffic going through only this port? </p>