java write netstat in cmd

Question

My goal is to print all the internet connections on my computer. When I type netstat on CMD, I get the internet connections list. I wanted to do the same in Java, automatically.

My code:

Runtime runtime = Runtime.getRuntime();
process = runtime.exec(pathToCmd);
byte[] command1array = command1.getBytes(); // writing netstat in an array of bytes
OutputStream out = process.getOutputStream();
out.write(command1array);
out.flush();
out.close();
readCmd();  //read and print cmd

But with this code I get C:\eclipse\workspace\Tracker>Mais? instead of the list of connections. Obviously I'm working with Eclipse, in Windows 7. What am I doing wrong? I've looked in similar topics but I couldn't find what's wrong. Thank you for the answers.

EDIT:

public static void readCmd() throws IOException {
    is = process.getInputStream();
    isr = new InputStreamReader(is);
    br = new BufferedReader(isr);
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
}

you should use `ProcessBuilder` instead of `Runtime` and you need to show us `readCmd()`. the error probably lies in there. — Zhedar, Mar 31 '13 at 22:38
alright, `readCmd` seems ok. maybe just try to use a `PrintWriter` wrapping your `OutputStream`. I also encountered this problem some time ago. Still don't know, why that happens. — Zhedar, Mar 31 '13 at 22:47
"Obviously i'm working with eclipse, in windows 7" - how is that obvious? — eis, Nov 14 '21 at 23:03

score 0 · Answer 1 · answered Apr 02 '13 at 20:38

Try this : I was able to create a file in my default temporary directory with all the connections

final String cmd = "netstat -ano";

        try {

            Process process = Runtime.getRuntime().exec(cmd);

            InputStream in = process.getInputStream();

            File tmp = File.createTempFile("allConnections","txt");

            byte[] buf = new byte[256];

            OutputStream outputConnectionsToFile = new FileOutputStream(tmp);

            int numbytes = 0;

            while ((numbytes = in.read(buf, 0, 256)) != -1) {

                outputConnectionsToFile.write(buf, 0, numbytes);

            }

            System.out.println("File is present at "+tmp.getAbsolutePath());


        } catch (Exception e) {
            e.printStackTrace(System.err);
        }

You forgot to close the file. – user207421 Mar 23 '20 at 01:12 — user207421, Mar 23 '20 at 01:12

score 0 · Answer 2 · answered Jul 11 '23 at 07:29

File NETSTAT.EXE should be on the PATH (environment variable), hence your "command" of just netstat should be enough. If NETSTAT.EXE is not on the PATH, you can either edit the PATH or provide the full path to the file in your Java code. On my Windows 10 machine, the path to the file is...

C:\Windows\System32\NETSTAT.EXE

You should also use class ProcessBuilder rather than class Runtime. Since JDK 7, class ProcessBuilder has method inheritIO. Hence if all you want is to print the output of netstat, the following is the simplest code to achieve that. Note that the below code works because file NETSTAT.EXE is on the PATH.

import java.io.IOException;

public class Solution {
    public static void main(String[] args) {
        ProcessBuilder pb = new ProcessBuilder("netstat");
        pb.inheritIO();
        try {
            pb.start();
        }
        catch (IOException x) {
            x.printStackTrace();
        }
    }
}

Here are the first few lines of output that are displayed when I run the above code.


Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    127.0.0.1:5354         BDL-DLRC88V:49669      ESTABLISHED

score -1 · Answer 3 · answered Apr 04 '14 at 16:47

-1

You can also use an instance of java.util.Scanner to read the output of the command.

public static void main(String[] args) throws Exception {
    String[] cmdarray = { "netstat", "-o" };
    Process process = Runtime.getRuntime().exec(cmdarray);
    Scanner sc = new Scanner(process.getInputStream(), "IBM850");
    sc.useDelimiter("\\A");
    System.out.println(sc.next());
    sc.close();
}

answered Apr 04 '14 at 16:47

Paul Vargas

41,222
15
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The problem isn't parsing the output, it is getting the correct output, i.e. running the correct command. – user207421 Mar 23 '20 at 01:13

score -2 · Answer 4 · edited Apr 10 '18 at 21:32

-2

final String cmd = "netstat -ano";

    try {

        Process process = Runtime.getRuntime().exec(cmd);

        InputStream in = process.getInputStream();
        InputStreamReader isr = new InputStreamReader(in);
        BufferedReader br = new BufferedReader(isr);
        String line;

        while ((line = br.readLine()) != null) {
           System.out.println(line);
        }


    } catch (Exception e) {
        e.printStackTrace(System.err);
    } finally{
        in  = null;
        isr = null;
        br = null;
    }

edited Apr 10 '18 at 21:32

rollstuhlfahrer

3,988
9
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answered Apr 10 '18 at 21:07

Santosh Kumar

1

2

While this code may answer the question, providing additional context regarding why and/or how this code answers the question improves its long-term value. – rollstuhlfahrer Apr 10 '18 at 21:32

java write netstat in cmd

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