Android客户端未收到服务器回复

我有一个Android客户端，可将数据发送到Java服务器。经过一些服务器处理后，我希望服务器回复给客户端，但是我无法上班。

最初，客户端和服务器都卡在上readLine()，因此我添加\n了两者，但仍然没有变化。经过长时间的搜索后，我尝试关闭客户端连接，然后服务器运行，但是客户端给出了错误，因为套接字已关闭。正确的方法是什么？为什么？

客户代码：

private class sendToServer extends AsyncTask<JSONObject, Void, String> {
    @Override
    protected String doInBackground(JSONObject... userData) {
        Socket clientSocket;
        try {
            clientSocket = new Socket("10.0.2.2", 7878);
            BufferedOutputStream  outToServer = new BufferedOutputStream(clientSocket.getOutputStream());
            outToServer.write( (userData[0].toString() + '\n').getBytes() );
            outToServer.flush();

            BufferedReader inFromServer = new BufferedReader(new Inpu    tStreamReader(clientSocket.getInputStream()));
            String reply = inFromServer.readLine();

            outToServer.close();
                Log.d("",reply);

            inFromServer.close();
            clientSocket.close();

        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

服务器代码：

@Override
public void run() {
    try {
        BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        StringBuilder builder = new StringBuilder();
        String line;
        while ((line = inFromClient.readLine()) != null)
                builder.append(line);

        BufferedOutputStream outToClient = new BufferedOutputStream(connection.getOutputStream());
        outToClient.write( ("ACK" + '\n').getBytes() );
        outToClient.flush();

            inFromClient.close();           
            putToClient.close();

        parseIncomingData(builder.toString());

    } catch (Exception e) {
        System.out.println(e);
    } finally {
        try {
            connection.close();
        } catch (IOException e) {
            System.out.println(e);
        }
    }
}