问无法连接到端口7

EN

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

public class EchoClient {
    public static void main(String[] args) throws Exception {
        Socket echoSocket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        try {
            echoSocket = new Socket("localhost", 7);
            out = new PrintWriter(echoSocket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(
                                        echoSocket.getInputStream()));
        } catch (Exception e) {
            System.err.println(e.getMessage());
            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();
    }
}