question regarding Echoclient program

I am always getting the message Don't know about host: taranis. while running echoclient program. here is the program below

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

public class EchoClient {
    public static void main(String[] args) throws IOException {

        Socket echoSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;

        try {
            echoSo开发者_Go百科cket = new Socket("taranis",3218);
            out = new PrintWriter(echoSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(
                                        echoSocket.getInputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Don't know about host: taranis.");
            System.exit(1);
        } catch (IOException e) {
            System.err.println("Couldn't get I/O for "
                               + "the connection to: taranis.");
            System.exit(1);
        }

    BufferedReader stdIn = new BufferedReader(
                                   new InputStreamReader(System.in));
    String userInput;

    while ((userInput = stdIn.readLine()) != null) {
        out.println(userInput);
        System.out.println("echo: " + in.readLine());
    }

    out.close();
    in.close();
    stdIn.close();
    echoSocket.close();
    }
}

You need to use a valid host name, or a valid IP of your server (assuming you have one) when you initialize your socket (new Socket("taranis",3218) ). It is great to take those tutorials (as pointed by icktoofay), but especially when it comes to networking, you have to make sure you have the matching application running on the other side, and that the parameters match it. IP and port usually change from machine to machine and from application to application.