套接字程序无法通过第一次消息交换

Question

我正在尝试用Java构建一个简单的客户端 - 服务器套接字程序，其中交换基本信息。但是，只有第一条消息似乎在客户端和服务器之间传递，之后程序挂起。我展示了相关的代码。我提前道歉，但我从来没有使用Java或任何其他语言进行任何大量的套接字编程工作。

public static void main(String[] args) {
    (new Thread(new SeederServer())).start();

    for (int i=0; i < 1; ++i) {
        (new Thread(new SeederClient())).start();
    }
}

public class SeederServer implements Runnable {
    Set<String> set = Collections.synchronizedSet(new HashSet<String>());

    @Override
    public void run() {
        ServerSocket myServer = null;
        Socket clientSocket = null;

        try {
            myServer = new ServerSocket(SeederMain.serverPort);
            System.out.println(myServer.toString());
        }
        catch (IOException e) {
            System.out.println(e);
        }

        while (true) {
            try {
                clientSocket = myServer.accept();
            }
            catch (IOException e) {
                System.out.println(e);
            }
            new Thread(new SocketRunnable(clientSocket, set)).start();
        }
    }
}

public class SeederClient implements Runnable {
    private Socket client = null;

    @Override
    public void run() {
        try {
            client = new Socket("localhost", SeederMain.serverPort);
        }
        catch (IOException e) {
            System.out.println(e);
        }

        try {
            BufferedReader in =
                    new BufferedReader(
                            new InputStreamReader(client.getInputStream()));
            PrintStream os = new PrintStream(client.getOutputStream());
            os.println(SeederMain.HELLO);

            String line = in.readLine();
            System.out.println("socket " + client.getLocalPort() + " received response: " + line);

            for (int i=0; i < 10000; ++i) {
                os.println(SeederMain.GET_LIST);
                line = in.readLine();
                if (line != null) {
                    System.out.println("socket " + client.getLocalPort() + " received response: " + line);
                }
            }
            in.close();
            os.close();
        }
        catch (IOException e) {
            System.out.println(e);
        }
    }
}

public class SocketRunnable implements Runnable{
    private Socket clientSocket = null;
    private String serverText   = null;
    private Set<String> nodeSet;

    public SocketRunnable(Socket clientSocket, Set<String> nodeSet) {
        this.clientSocket = clientSocket;
        this.nodeSet = nodeSet;
    }

    public void run() {
        try {
            BufferedReader in =
                    new BufferedReader(
                            new InputStreamReader(clientSocket.getInputStream()));
            OutputStream out = clientSocket.getOutputStream();
            String input = in.readLine();
            String output = "";
            if (input.equals(SeederMain.HELLO)) {
                nodeSet.add(String.valueOf(clientSocket.getLocalPort()));
                output = SeederMain.HELLO;
            }
            else if (input.equals(SeederMain.GET_LIST)) {
                output = nodeSet.toString();
            }
            else {
                output = SeederMain.ERROR;
            }
            out.write(output.getBytes());
            out.close();
            in.close();
        } catch (IOException e) {
            //report exception somewhere.
            e.printStackTrace();
        }
    }
}