Is there a way to find a port being used by process, given its process id , using java?

Question

Is there a way to find a port opened by java process, given the process id of the process in java? Need to find it using java as it has to be platform independent

Given a process id : output any port/socket connections being used by that process.

Few things given: Process running in same jvm. There is only 1 port/socket being used by that Process, for which the Pid is given.

Can not do platform specific commands like ps -au | grep pid | ...

score 2 · Answer 1 · answered Sep 03 '11 at 02:11

2

The answer is no. What processes have what ports is not information available to java applications at all. You'd need JNI and it would depend on the operating system.

answered Sep 03 '11 at 02:11

bmargulies

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What about `lsof -i` executed in runtime? – Bohemian Sep 03 '11 at 04:11
1

That's not 100% Java. It's all system calls and /proc files -- and we might be on Windows here. – bmargulies Sep 03 '11 at 18:48

score 1 · Answer 2 · 2011-09-03T09:43:21.030

1

Have you tried jps? See http://download.oracle.com/javase/1.5.0/docs/tooldocs/share/jps.html

Would it help if you put the port number into the current thread name, then you could extract the port number from the thread name? e.g.

import java.net.ServerSocket;

public class SocketDriver { 
    public static void main(String[] args) throws Exception {       
        ServerSocket serverSocket = new ServerSocket(0);
        int localPort = serverSocket.getLocalPort();

        String threadName = Thread.currentThread().getName(); 
        Thread.currentThread().setName(threadName + ":" + localPort);
        System.out.println("port -> " + localPort);
        System.out.println("thread -> " + Thread.currentThread().getName());
        serverSocket.close();
    }
}

Output is:

port -> 51958
thread -> main:51958

edited Sep 03 '11 at 09:43

answered Sep 02 '11 at 22:09

thanks just tried it. quite close to what I needed. but jps shows only the explicitly set parameters. I have a port being opened dynamically using new ServerSocket(0). Need to figure out what is the port which got created. JPS falls short there. thanks for help. – Devesh Sep 02 '11 at 22:52
glad it helped, did you write the server? why do you need the port number? just curious – Sep 02 '11 at 23:01
yes, it is needed in a server which starts at a port. The free port is discovered at run time using new ServerSocket(0) and it needs to be able to process JMX commands later (refresh , shutdown etc.). This is where the real port number is needed. The process is known by now. Any suggestions for finding the port number, given the process id? – Devesh Sep 03 '11 at 00:25

score 1 · Answer 3 · answered Sep 03 '11 at 04:10

1

The answer is yes, depending on your operating system.

You need to find the appropriate command, for example on mac osx, it's lsof -i, then use Runtime to execute it and parse the output.

Here's some basic code that would do it:

 Process p = Runtime.getRuntime().exec(new String[] { "lsof", "-i" });
 InputStream commandOutput = p.getInputStream();

answered Sep 03 '11 at 04:10

Bohemian

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Know of any util that captures all of the cross platform complexity under a nice API? – oligofren Jun 01 '21 at 10:48
@TheNimbleSurfer no, but there are basically only 2 OS flavours, so you could [determine the OS](https://stackoverflow.com/questions/228477/how-do-i-programmatically-determine-operating-system-in-java) then use either `lsof` or [the windows equivalent](https://stackoverflow.com/a/599268/256196) – Bohemian Jun 01 '21 at 22:28

Is there a way to find a port being used by process, given its process id , using java?

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