Question

我正在尝试将TCP与Android应用程序一起使用，因此有两个项目，一个是服务器，另一个是客户端。当我运行服务器并打开客户端时，一切正常并且消息正在传递给双方，但是当我关闭应用程序（从模拟器）时，它不会在控制台中提醒我套接字连接已关闭且尝试获取另一个连接，以便在尝试重新打开应用程序时，它不会重新连接，也不会传递消息。

那我在这里做错了什么？我是Android和TCP的新手，所以如果这是一个非常新的问题，我很抱歉。

@Override
public void run() {
    super.run();

    running = true;

    try {
        System.out.println("S: Connecting...");

        //create a server socket. A server socket waits for requests to come in over the network.
        ServerSocket serverSocket = new ServerSocket(SERVERPORT);

        //create client socket... the method accept() listens for a connection to be made to this socket and accepts it.
        while (running) {
            Socket client = serverSocket.accept();

            try {

                //sends the message to the client
                mOut = new PrintWriter(new BufferedWriter(new OutputStreamWriter(client.getOutputStream())), true);

                //read the message received from client
                BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));

                //in this while we wait to receive messages from client (it's an infinite loop)
                //this while it's like a listener for messages
                while(!client.isClosed()) {
                    String message = in.readLine();
                    if (message != null && messageListener != null) {
                        //call the method messageReceived from ServerBoard class
                        messageListener.messageReceived(message);
                    }
                }


            } catch (Exception e) {
                System.out.println("S: Error");
                e.printStackTrace();
            } finally {
                client.close();
                System.out.println("S: Done.");
            }
      }

    } catch (Exception e) {
        System.out.println("S: Error");
        e.printStackTrace();
    }

}

Answer 1

It would be more accurate to say that you aren't testing for disconnection correctly.

Socket.isClosed() does not magically become true when the peer disconnects. So using it to control a read loop is futile. It only tells you whether you have closed this socket.
readLine() returns null when the peer has disconnected, but you're treating it as just another value.

A correct loop using readLine() looks like this:

while ((line = in.readLine()) != null)
{
    // ...
}

Android TCP - 应用程序关闭时Socket不会断开连接

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