CMD-找不到Java套件

Question

我正在尝试通过Eclipse用Java编写客户端服务器应用程序。这是代码：

package edu.fcps.ab;
import java.io.*;
import java.net.*;
import java.util.*;

public class TestServer {
    public static Vector<String> messages = new Vector<String>();
    public static void main (String args[]) {
        Scanner scan = new Scanner(System.in);
        System.out.println("Enter port number");
        int port = scan.nextInt();
        try {
            ServerSocket serverSock = new ServerSocket(port);
            Socket s = serverSock.accept();
            int messageLength = 0;
            PrintWriter output = new PrintWriter(s.getOutputStream());
            BufferedReader input = new BufferedReader(new InputStreamReader(s.getInputStream()));
            String inputLine;
            while(true) {
                if(messages.size() > messageLength) {
                    for(int i = messageLength; i < messages.size(); i++) {
                        System.out.println(messages.get(i));
                    }
                    messageLength = messages.size();
                }
            }
        } catch(Exception e) {
            System.out.println("An error occurred");
        }

    }
}

package edu.fcps.ab;
import java.io.*;
import java.net.*;
import java.util.*;
public class TestClient implements Runnable{
    public static void main (String args[]) {
        TestClient tc = new TestClient();
        Thread t = new Thread(tc);
        t.start();
    }

    @Override
    public void run() {
        Scanner s = new Scanner(System.in);
        System.out.println("Enter port");
        int port = s.nextInt();
        String ip = "127.0.0.1";
        try {
            Socket sock = new Socket(ip, port);
            System.out.println("Successfully connected");
            System.out.println("Enter username");
            String username = s.next();
            PrintWriter out = new PrintWriter(sock.getOutputStream(), true);
            BufferedReader input = new BufferedReader(new InputStreamReader(sock.getInputStream()));
            BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
            String sent;
            while(true) {
                sent = stdin.readLine();
                if(sent != null) {
                    TestServer.messages.add(username + ": " + sent);
                }
            }
        } catch(Exception e) {
            e.printStackTrace();
        }
    }
}

代码在Eclipse中可以正常编译，但是当我尝试通过命令行编译客户端时，出现此错误：

TestClient.java:31: error: package TestServer does not exist
                                        TestServer.messages.add(username + ": " + sent);

服务器和客户端文件在同一程序包中。为什么会发生此错误，我该如何解决？