Java.lang.SecurityManager.checkListen() Method



The java.lang.SecurityManager.checkListen(int port) method throws a SecurityException if the calling thread is not allowed to wait for a connection request on the specified local port number.

If port is not 0, this method calls checkPermission with the SocketPermission ("localhost:"+port,"listen"). If port is zero, this method calls checkPermission with SocketPermission("localhost:1024-","listen"). If you override this method, then you should make a call to super.checkListen at the point the overridden method would normally throw an exception.


Following is the declaration for java.lang.SecurityManager.checkListen() method

public void checkListen(int port)


  • port -- the local port.

Return Value

This method does not return a value.


  • SecurityException -- if the calling thread does not have permission to listen on the specified port.


Our examples require that the permissions for each command is blocked. A new policy file was set that allows only the creating and setting of our Security Manager. The file is in C:/java.policy and contains the following text:

grant {
  permission java.lang.RuntimePermission "setSecurityManager";
  permission java.lang.RuntimePermission "createSecurityManager";
  permission java.lang.RuntimePermission "usePolicy";

The following example shows the usage of lang.SecurityManager.checkListen() method.

package com.tutorialspoint;

public class SecurityManagerDemo extends SecurityManager {

   // checkListen needs to be overriden
   public void checkListen(int port) {
   throw new SecurityException();

   public static void main(String[] args) {

   // set the policy file as the system securuty policy
   System.setProperty("", "file:/C:/java.policy");

   // create a security manager
   SecurityManagerDemo sm = new SecurityManagerDemo();

   // set the system security manager

   // perform the check

   // print a message if we passed the check

Let us compile and run the above program, this will produce the following result:

Exception in thread "main" java.lang.SecurityException