java - Android Tcp 客户端检查与服务器的连接

Question

嗨，我有一个 Tcp 客户端，我想检查他是否连接到服务器，我不是要检查他是否连接到 socket.isConnected() 或 socket.isBound() 我的意思是我想知道如果套接字现在已连接，但我找不到方法，因为当服务器断开连接时，他不会向客户端发送任何内容

这是我的代码:

    public void sendMessage(String message) {
    if (out != null && !out.checkError()) {
        out.println(message);
        out.flush();
    }
}

public void stopClient() {
    mRun = false;
}

public void run() {

    mRun = true;
    try {
        //connecting
        InetAddress serverAddr = InetAddress.getByName(SERVERIP);
        Socket socket = new Socket(serverAddr, SERVERPORT);
        sss = socket;


        try {
            //send the message to the server
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
            //receive the message that the server sends back
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            HelloService.firstTouch();


            //in this while the client listens for the messages sent by the server
            while (mRun) {
                serverMessage = in.readLine();

                if (serverMessage != null && mMessageListener != null) {
                    //call the method messageReceived from MyActivity class to inform main activity that a message has received
                    mMessageListener.messageReceived(serverMessage);
                }
                serverMessage = null;
            }

        } catch (Exception e) {

        } finally {

            socket.close();
        }

    } catch (Exception e) {

    }
}

Answer 1

当服务器断开连接时，readLine() 返回 null，您需要检查它，并在获取到连接时跳出读取循环并关闭连接。您目前的检查仅足以避免 NPE。