title: Reserved TCP/IP ports
body: <p>Do reserved TCP/IP ports require that a program is running and bound to the port? If no such program is running or exists, can another program use this port? For example, on Linux, port 7 is reserved for an echo server. I assume there is some program running and is bound to port 7 of the machine. The program basically echos back input. If this program is stopped, will port 7 be released? </p>
  
  <p>If I wrote my own echo server and bound it to some other port, wouldn't this port be released once my custom echo server program is killed?</p>
  
  <p>Does the same thing happen for reserved ports?</p>
  
  <p>Also, if all these programs are running on reserved ports, wouldn't they consume system resources even if they are blocked listening for a connection? Are these programs running at all times? </p>