how to run this program successfully?...this has an ERROR

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

class AdviceClient
{
void go()
{
try
{
Socket s = new Socket("127.0.0.1",4242);

InputStreamReader ir = new InputStreamReader(s.getInputStream());
BufferedReader br = new BufferedReader(ir);

String str=br.readLine();
System.out.println("Advice = " + str);
br.close();
}catch(Exception e)
{
e.printStackTrace();
}

}
public static void main(String args[])
{
AdviceClient obj = new AdviceClient();
obj.go();
}
}

my system is also connected to net but still error
any suggestions with reason...
ERROR:
java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at AdviceClient.go(AdviceClient.java:10)
at AdviceClient.main(AdviceClient.java:27)