Question

我是java TCP套接字的新手。我试图实现一个服务器和一个客户端。所以服务器应检查输入（做某事）并将字符串发送到客户端。客户端应该将字符串发送到服务器并从服务器中查找输入字符串（并执行某些操作）。如果有新的可用内容，它们都应该循环检查并一直发送。客户端可以将数据发送到服务器，服务器接收它可以显示/处理该数据。但是客户端不显示来自服务器的数据。有人能告诉我为什么客户端没有从服务器接收字符串？有没有更好的想法做无限循环？将只有一个客户端和一个服务器。

 while true:
 server out------>  send String----->   in client            
        in<-----  sent String <------   out

这是简化的服务器部分：

public class MainActivity extends Activity {
Socket client;
ServerSocket server;
int serverport = 54321;
String inputData = null;
BufferedReader in;
PrintWriter out;
String outputData;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new Thread(setupConnection).start();    
}

private Runnable setupConnection = new Thread() {
public void run() {
try {
server = new ServerSocket(serverport);
    while (true) {
    client = server.accept();
    in = new BufferedReader(new InputStreamReader(client.getInputStream()));
    out = new PrintWriter(client.getOutputStream(), true);
    inputData = in.readLine();
    InputStream inStream = new ByteArrayInputStream(inputData.getBytes());
    in.close();
        if (inputData != null) {
        System.out.println(TAG + "-----Incoming Message---- " + inputData);
        //this is working String is shown           
        }       }
    out.write("nothing to do?");
    out.flush();
    out.close();
    }

} catch (SocketException e) {
Log.v(TAG, "SocketException: " + e);
e.printStackTrace();
} catch (IOException e) {
Log.v(TAG, "IOException: " + e);
e.printStackTrace();
}
}

简化的客户端如下所示：

public class testClass {
public static void main(String[] args) throws IOException, InterruptedException {
Socket socket = null;
String host = "127.0.0.1";
int port = 54321;
PrintWriter out = null;
BufferedReader in = null;

while (true) {
try {
    socket = new Socket(host, port);
    out = new PrintWriter(socket.getOutputStream(), true);
    in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
} catch (UnknownHostException e) {
    System.out.println(TAG + "Error: " + e);
    System.err.println("Don't know about host: localhost.");
    System.exit(1);
} catch (IOException e) {
    System.out.println(TAG + "Error: " + e);
    System.err.println("Couldn't get I/O for " + "the connection to: localhost.");
    System.exit(1);
}

out.println("Hello, is it me you're looking for...");
out.flush();


String input = in.readLine();
System.out.println("Input: " + input);

in.close();
out.close();

}
}
}

Answer 1

如果readLine（）返回null，则对等体已关闭连接，您必须这样做。并停止阅读。

Answer 2

如果你想在android中实现这个代码，你会遇到很多问题：你可以在这个链接中找到解决方案： Post JSON in android

以下代码中的

可能会解决此问题：

    HttpPost post = new HttpPost("http://xxxxxx");
    DefaultHttpClient httpClient = new DefaultHttpClient();
    post.setEntity(new ByteArrayEntity(json.toString().getBytes()));
    HttpResponse response = httpClient.execute(post);
    return EntityUtils.toString(response.getEntity());

} catch (UnsupportedEncodingException e) {
    e.printStackTrace();
    System.out.println(">>>>>>>" + e.getMessage());
} catch (ClientProtocolException e) {
    e.printStackTrace();
    System.out.println(">>>>>>>" + e.getMessage());
} catch (IOException e) {
    e.printStackTrace();
    System.out.println(">>>>>>>" + e.getMessage());
}

Java：TCP套接字连接。接收null / readline（）的客户端返回null

2 个答案: