子プロセスで開いているポートに親プロセスからconnectする

Child.java

import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;

public class Child {

    public static void main(String[] args) throws Exception {
        try (ServerSocket sock = new ServerSocket()) {
            sock.bind(new InetSocketAddress(41000));
            while (true) {
                System.err.println("CHILD: accepting");
                try (Socket client = sock.accept()) {
                    InputStream i = client.getInputStream();
                    byte[] buf = new byte[1024];
                    int len = i.read(buf);
                    System.err.println("CHILD: receive message: " + new String(buf, 0, len));

                    OutputStream o = client.getOutputStream();
                    o.write("hi, i am client".getBytes());
                    o.flush();
                }
            }
        }
    }
}

Parent.java

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ProcessBuilder.Redirect;
import java.net.InetSocketAddress;
import java.net.Socket;

public class Parent {

    public static void main(String[] args) throws Exception {
        String javahome = System.getProperty("java.home");
        String classpath = System.getProperty("java.class.path");
        ProcessBuilder pb = new ProcessBuilder(javahome + "/bin/java", "-cp", classpath, "Child");
        pb.redirectError(Redirect.INHERIT);

        Process p = pb.start();
        try {
            for (int i = 0; i < 10; ++i) {
                try (Socket s = new Socket()) {
                    System.out.println("PARENT: connect, try " + (i + 1));
                    try {
                        s.connect(new InetSocketAddress("localhost", 41000));
                    }
                    catch (IOException e) {
                        if (i == 9)
                            throw e;

                        Thread.sleep(1000);
                        continue;
                    }

                    OutputStream o = s.getOutputStream();
                    o.write("i am parent".getBytes());
                    o.flush();

                    InputStream in = s.getInputStream();
                    byte[] buf = new byte[1024];
                    int len = in.read(buf);
                    System.out.println("PARENT: receive message: " + new String(buf, 0, len));
                    break;
                }
            }
        }
        finally {
            p.destroy();
        }
    }
}