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Groups > comp.lang.java.programmer > #39742

Re: what thread or module is listening on a port?

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On 23/02/2022 18:15, Arne Vajhøj wrote:
> On 2/23/2022 7:37 AM, Andreas Leitgeb wrote:
>> Given a java process (that uses a couple of 3rd-party libs and stuff from
>> maven repo) and a TCP port number that this process is listening on 
>> (for all
>> interfaces), what options do I have for finding out, which "part" of the
>> process is responsible for the listening port?
>>
>> Once I see, which of the umpty libraries did it, I can look for options
>> to either unconfigure it, bind to localhost, or at least understand it.
>>
>> That's on Solaris (Unix).
>> $ netstat -aun | grep "54157.*LISTEN"     # gives me e.g:
>>        *.52634              *.*            xxx  54157 java 0      0  
>> 256000      0 LISTEN
>>
>> The portnumber is in the >32k range and changes with each restart
>> of the process, thus apparently isn't itself configured.
>>
>> When I telnet to the port, the connection is dropped after writing any 6
>> bytes to it. - maybe that rings a bell for some type of common service?
>>
>> PS: Java here is Azul's "Zulu", openjdk version 1.8.0_252
>>       (in case it matters for further diagnostic tools available)
> 
> You could track all locations opening a socket.
> 
> Demo:
> 
> package february;
> 
> import java.io.IOException;
> import java.lang.reflect.Constructor;
> import java.net.ServerSocket;
> import java.net.SocketImpl;
> import java.net.SocketImplFactory;
> import java.util.Arrays;
> import java.util.stream.Collectors;
> 
> public class SocketTrace {
>      public static void enableTrace() throws IOException {
>          ServerSocket.setSocketFactory(new SocketImplFactory() {
>              @Override
>              public SocketImpl createSocketImpl() {
>                  Exception e = new Exception();
>                  StackTraceElement[] ste = e.getStackTrace();
>                  String trace = Arrays.stream(ste).skip(4).map(v -> 
> v.getClassName() + "." + v.getMethodName()).collect(Collectors.joining(" 
> "));
>                  System.out.printf("socket opened from %s\n", trace);
>                  try {
>                      Class<?> stdimpl = 
> Class.forName("java.net.SocksSocketImpl");
>                      Constructor<?> ctor = 
> stdimpl.getDeclaredConstructor();
>                      ctor.setAccessible(true);
>                      return (SocketImpl) ctor.newInstance();
>                  } catch(Exception ex) {
>                      throw new RuntimeException(ex);
>                  }
>              }
>          });
>      }
>      public static void m3() throws IOException {
>          ServerSocket s = new ServerSocket(12345);
>          s.close();
>      }
>      public static void m2() throws IOException {
>          m3();
>      }
>      public static void m1() throws IOException {
>          m2();
>      }
>      public static void main(String[] args) throws IOException {
>          enableTrace();
>          m3();
>          m2();
>          m1();
>      }
> }
> 
> output:
> 
> socket opened from february.SocketTrace.m3 february.SocketTrace.main
> socket opened from february.SocketTrace.m3 february.SocketTrace.m2 
> february.SocketTrace.main
> socket opened from february.SocketTrace.m3 february.SocketTrace.m2 
> february.SocketTrace.m1 february.SocketTrace.main
> 
> Arne
> 

That's bloody brilliant!

-- 
DF.

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Thread

what thread or module is listening on a port? Andreas Leitgeb <avl@logic.at> - 2022-02-23 12:37 +0000
  Re: what thread or module is listening on a port? Eric Sosman <esosman@comcast-dot-net.invalid> - 2022-02-23 10:51 -0500
    Re: what thread or module is listening on a port? Martin Gregorie <martin@mydomain.invalid> - 2022-02-23 16:51 +0000
  Re: what thread or module is listening on a port? Arne Vajhøj <arne@vajhoej.dk> - 2022-02-23 12:15 -0500
    Re: what thread or module is listening on a port? Andreas Leitgeb <avl@logic.at> - 2022-02-24 23:04 +0000
    Re: what thread or module is listening on a port? Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2022-03-19 12:47 +0100

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