Question

I have the java app with a custom security policy and when I tried to open 100 udp sockets I've got exception:

java.net.SocketException: maximum number of DatagramSockets reached

Test app:

import java.net.DatagramSocket;
import java.net.Inet4Address;
import java.util.ArrayList;
import java.util.List;   

public class Test {
    static int basePortNum = 40000; 
    public static void main(String[] args) {
        List<DatagramSocket> socks = new ArrayList<DatagramSocket>();
        try{
            for(int i = 0; i<100; i++){
                socks.add(new DatagramSocket(basePortNum+i, Inet4Address.getByName("127.0.0.1")) );
                System.out.println(i);
            }
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            for(java.net.DatagramSocket soc: socks){
                soc.close();
            }
        }    
    }    
}

If I launch it without security manager it creates all 100 sockets:

0
1
...
98
99

But if I add this line to VM arguments

-Djava.security.manager

It fails even with default security policy:

0
1
...
23
24
java.net.SocketException: maximum number of DatagramSockets reached
    at sun.net.ResourceManager.beforeUdpCreate(ResourceManager.java:53)
    at java.net.PlainDatagramSocketImpl.create(PlainDatagramSocketImpl.java:74)
    at java.net.DatagramSocket.createImpl(DatagramSocket.java:318)
    at java.net.DatagramSocket.<init>(DatagramSocket.java:209)
    at java.net.DatagramSocket.<init>(DatagramSocket.java:262)
    at Test.main(Test.java:16)

How can I change socket limit while using security manager?

UPD: it was reproduced on windows 8.1 x64, windows 7 x64 and windows xp sp3 x32, windows 7 x32. On all systems JDK 1.6.45 x32 was used.

UPD2: on windows xp sp3 x32 reproduced with JDK7 too, but can't reproduce this with JDK 1.6.27.

UPD3: debugging JDK classes found this:

// Compiled from ResourceManager.java (version 1.5 : 49.0, super bit)
public class sun.net.ResourceManager {

  // Field descriptor #14 I
  private static final int DEFAULT_MAX_SOCKETS = 25;

In open JDK implementation the default socket limit is 1024 http://www.docjar.com/html/api/sun/net/ResourceManager.java.html

Was it helpful?

Solution

That VM argument helped:

-Dsun.net.maxDatagramSockets=101

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