我在Java中编写了一个简单的TCP-client类。它用于连接到用Python编写的TCP服务器,并在新线程中处理传入的消息。它看起来像这样:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.Socket;
public class TCPTestClient {
private String mHost;
private int mPort;
private Socket mSocket;
private PrintWriter mWriter;
private BufferedReader mReader;
public TCPTestClient(String host, int port) {
mHost = host;
mPort = port;
}
public void connect() throws IOException {
if (mSocket == null || mSocket.isClosed()) {
mSocket = new Socket();
mSocket.connect(new InetSocketAddress(mHost, mPort), 5000);
mWriter = new PrintWriter(mSocket.getOutputStream());
mReader = new BufferedReader(new InputStreamReader(mSocket
.getInputStream()));
new Thread(new InputHandler(mReader, this)).start();
}
}
public void close() throws IOException {
if (mSocket != null && !mSocket.isClosed()) {
mSocket.close();
}
}
class InputHandler implements Runnable {
BufferedReader mReader;
TCPTestClient mClient;
public InputHandler(BufferedReader reader, TCPTestClient client) {
mReader = reader;
mClient = client;
}
public void run() {
String line = null;
try {
while ((line = mReader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
如果新客户端已连接或断开连接,TCP服务器只会将“客户端连接”和“客户端断开连接”打印到stdout。在普通的java应用程序中运行TCPTestClient时,这很有用:连接在调用connect()时建立,在调用close()时关闭,并且InputHandler中的等待readLine()因为SocketException说套接字是关闭(java.net.SocketException: Socket closed
)。这是我预期的行为。
但是当我在Android上运行此代码时,连接将不会被关闭:readLine()仍会阻塞而不会抛出SocketException,并且服务器不显示“客户端已断开连接”消息。
这是我的活动:
import java.io.IOException;
import android.app.Activity;
import android.util.Log;
public class Foo extends Activity {
private TCPTestClient mClient;
private static final String TAG = "Foo";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.foo);
mClient = new TCPTestClient("192.168.1.2", 3456);
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG, "onPause");
try {
mClient.close();
} catch (IOException e) {
Log.d(TAG, "Disconnect failed", e);
}
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume");
try {
mClient.connect();
} catch (IOException e) {
Log.d(TAG, "Connect failed", e);
}
}
}
因此,当Activity启动/恢复时,将建立连接。当用户点击后退按钮时,应该关闭连接。但是,调用onPause()和close(),但套接字未关闭,因为BufferedReader仍然阻塞等待Input。封闭方法中的mReader.close()
之类的调用也会阻止。
是否有人知道如何解决此问题,以便在暂停活动时成功关闭连接?
答案 0 :(得分:0)
您如何确认客户端套接字未关闭?
在服务器端检测已关闭连接的唯一可靠方法是写入数据,并在协议中添加心跳。
答案 1 :(得分:0)
是的,在2.3之前你必须使用mSocket.shutdownInput()和mSocket.shutdownOutput()来抛出异常。但目前在2.2.2中,它对我不起作用。 :(仍然找到一种抛出异常的方法。