root/test_projects/SocketChecker.java

import java.io.*;
import java.net.*;

class SocketChecker
{
        public static final void main( String args[] )
          {
             System.out.println("Begin Test");
             OpenSocket openSock= new OpenSocket();
             openSock.ServerStart(true);
          }
        static class OpenSocket
        {
                public OpenSocket(){
                        port=7055;
                }
                public void ServerStart(boolean onExStart){
                        if (onExStart==true){
                                try{
                                        int waitingsecond=30;//How many second is the socket wait.
                                        ServerSocket serverEx = new ServerSocket(port);
                                        serverEx.setSoTimeout(waitingsecond*1000);//setSoTimeout-input is milisecond.
                                        Socket connectionSock = serverEx.accept();
                                BufferedReader inSocket = new BufferedReader(new InputStreamReader(connectionSock.getInputStream()));
                                BufferedWriter outSocket = new BufferedWriter(new OutputStreamWriter(connectionSock.getOutputStream()));
                                String echoline=inSocket.readLine();
                                System.out.println(echoline);
                                outSocket.write(echoline);
                                outSocket.flush();
                                inSocket.close();
                                outSocket.close();
                                connectionSock.close();
                                        serverEx.isClosed();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                        }
                        else System.out.println("error");
                }
                private int port;
        }
}