在服务器套接字java中从客户端获取数据

我正在创建一个执行以下任务的服务器应用程序

• 接受客户端的连接
• 将每个客户端连接处理到单独的线程
• 接收来自客户端的数据
• 发送数据给客户端

我能够连接客户端，但无法从客户端接收数据

仅当该客户端断开连接时，数据才在我的控制台中可见..！！！

Code :-

public class ServerListener {

    public static void main(String[] args) {
        new ServerListener().startServer();
    }

    public void startServer() {
        final ExecutorService clientProcessingPool = Executors
                .newFixedThreadPool(10);

        Runnable serverTask = new Runnable() {
            @Override
            public void run() {
                try {
                    ServerSocket serverSocket = new ServerSocket(8000);
                    System.out.println("Waiting for clients to connect...");
                    while (true) {
                        Socket clientSocket = serverSocket.accept();
                        clientProcessingPool
                                .submit(new ClientTask(clientSocket));
                    }
                } catch (IOException e) {
                    System.err.println("Unable to process client request");
                    e.printStackTrace();
                }
            }
        };
        Thread serverThread = new Thread(serverTask);
        serverThread.start();
    }

    private class ClientTask implements Runnable {
        private final Socket clientSocket;

        private ClientTask(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }

        @Override
        public void run() {
            System.out.println("Got a client !");
            try {
            /* Get Data From Client */
                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(clientSocket.getInputStream()));
                String clientData = "";
                clientData = reader.readLine();
                System.out.println("Data From Client :" + clientData);

            /* Send Data To Client */

                //Code

                clientSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

您的实施存在问题

BufferedReader#readLine http://docs.oracle.com/javase/6/docs/api/java/io/BufferedReader.html#readLine():

读取一行文本。一行被视为由换行符 ('\n')、回车符 ('\r') 或回车符后紧跟换行符之一终止。

换句话说，如果您的客户从未发送过\nor \r字符该方法将不会结束，直到IOException由于断开连接而被抛出。

Solution

替换这段代码：

BufferedReader reader = new BufferedReader(
                    new InputStreamReader(clientSocket.getInputStream()));
String clientData = "";
clientData = reader.readLine();

with:

int red = -1;
byte[] buffer = new byte[5*1024]; // a read buffer of 5KiB
byte[] redData;
StringBuilder clientData = new StringBuilder();
String redDataText;
while ((red = clientSocket.getInputStream().read(buffer)) > -1) {
    redData = new byte[red];
    System.arraycopy(buffer, 0, redData, 0, red);
    redDataText = new String(redData,"UTF-8"); // assumption that client sends data UTF-8 encoded
    System.out.println("message part recieved:" + redDataText); 
    clientData.append(redDataText);
}
System.out.println("Data From Client :" + clientData.toString());

InputStream#read http://docs.oracle.com/javase/6/docs/api/java/io/InputStream.html#read(byte%5B%5D):

从输入流中读取一定数量的字节并将它们存储到缓冲区数组 b 中。实际读取的字节数以整数形式返回。此方法会阻塞，直到输入数据可用、检测到文件结尾或引发异常。

将在执行时读取尽可能多的字节 - 它基本上是缓冲读取。由于这些是原始字节，当将它们转换为字符串 http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#String(byte%5B%5D,%20java.nio.charset.Charset)您必须知道其编码才能正确显示它们（即“UTF-8”部分）。如果encoding http://en.wikipedia.org/wiki/Character_encoding其中您的客户端发送字节是其他的，您可能需要更改它才能在控制台输出中获得正确的文本。

我建议阅读官方教程：

• 字节流 http://docs.oracle.com/javase/tutorial/essential/io/bytestreams.html
• 字符流 http://docs.oracle.com/javase/tutorial/essential/io/charstreams.html
• 缓冲流 http://docs.oracle.com/javase/tutorial/essential/io/buffers.html