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Tip of the Day
Language: Java
Expertise: Beginner
Sep 15, 1998



Application Security Testing: An Integral Part of DevOps

Port information

I need to take a port number as input from a user. How can I check if the port number entered by the user is free and not being used by any program currently on his/her machine?

The only way to do this in pure Java is to try to open a socket on the local port and see if it succeeds. If it fails because the port number is already in use, then the connection attempt will throw a java.io.BindException. An example would look something like this:

ServerSocket socket;

try {
  socket = new ServerSocket(port);
} catch(BindException be) {
  // We failed because port was already in use
} catch(IOException ioe) {
  // Some other error happened
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