如何使用Canvas在图片周围旋转图片？(How would one rotate an image around itself using Canvas?)

 基本上，您希望打开与RTSP服务器主机名/端口的普通客户端套接字连接，然后发布RTSP OPTIONS请求。 如果服务器以“RTSP / 1.0 200 OK”响应，则表示流服务已启动，否则将关闭。 
 
 我写了一个快速而脏的样本RTSP检查并进行了测试。 随意根据您的需求进行调整： 
 
 更新处理UI操作在您的活动类中，创建以下字段： 
 
private static final int MESSAGE_RTSP_OK = 1;
private static final int MESSAGE_RTSP_ERROR = -1;

private Handler handler;
 
 在你的onCreate方法中，添加： 
 
    handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case MESSAGE_RTSP_OK:
                    //show_player(); 
                    // implement ui operation here
                    break;
                case MESSAGE_RTSP_ERROR:
                    //show_error();
                    break;
            }
        }
    };
 
 然后运行此示例代码： 更新了rtsp检查代码 
 
    new Thread() {
        public void run() {
            try {
                Socket client = new Socket("a1352.l1857053128.c18570.g.lq.akamaistream.net", 554);
                OutputStream os = client.getOutputStream();
                os.write("OPTIONS * RTSP/1.0\n".getBytes());
                os.write("CSeq: 1\n\n".getBytes());
                os.flush();

                //NOTE: it's very important to end any rtsp request with \n\n (two new lines). The server will acknowledge that the request ends there and it's time to send the response back.

                BufferedReader br =
                        new BufferedReader(
                                new InputStreamReader(
                                        new BufferedInputStream(client.getInputStream())));

                StringBuilder sb = new StringBuilder();
                String responseLine = null;

                while (null != (responseLine = br.readLine()))
                    sb.append(responseLine);
                String rtspResponse = sb.toString();
                if(rtspResponse.startsWith("RTSP/1.0 200 OK")){
                    // RTSP SERVER IS UP!!
                     handler.obtainMessage(MESSAGE_RTSP_OK).sendToTarget();
                } else {
                    // SOMETHING'S WRONG

                    handler.obtainMessage(MESSAGE_RTSP_ERROR).sendToTarget();
                }
                Log.d("RTSP reply" , rtspResponse);
                client.close();
            } catch (IOException e) {
                // NETWORK ERROR such as Timeout 
                e.printStackTrace();

                handler.obtainMessage(MESSAGE_RTSP_ERROR).sendToTarget();
            }

        }
    }.start();`
 
 在这个测试中，我选择了公共NASA TV rtsp服务器： rtsp://a1352.l1857053128.c18570.g.lq.akamaistream.net:554 
 
 代码发送以下rtsp请求： 
 
 OPTIONS * RTSP/1.0 CSeq: 1 
 
 并收到以下回复： 
 
 RTSP/1.0 200 OK Server: QTSS-Akamai/6.0.3 (Build/526.3; Platform/Linux; Release/Darwin; ) Cseq: 1 Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE, OPTIONS, ANNOUNCE, RECORD 
 
 如果您正在寻找更复杂的检查，请随时深入了解rtsp协议文档并根据您自己的需要增强代码： https ： //www.ietf.org/rfc/rfc2326.txt 
 
 如果需要更多信息，请告诉我。 

Basically you want to open a plain client socket connection to the RTSP server hostname/port and then post a RTSP OPTIONS request. If the server responds with a "RTSP/1.0 200 OK", it means the streaming service is up, otherwise it's down.
 
I wrote a quick and dirty sample RTSP check and tested it out. Feel free to adapt it to your needs:
 
Update handling UI operations In your activity class, create these fields:
 
private static final int MESSAGE_RTSP_OK = 1;
private static final int MESSAGE_RTSP_ERROR = -1;

private Handler handler;
 
in your onCreate method, add:
 
    handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case MESSAGE_RTSP_OK:
                    //show_player(); 
                    // implement ui operation here
                    break;
                case MESSAGE_RTSP_ERROR:
                    //show_error();
                    break;
            }
        }
    };
 
Then run this sample code: Updated rtsp check code
 
    new Thread() {
        public void run() {
            try {
                Socket client = new Socket("a1352.l1857053128.c18570.g.lq.akamaistream.net", 554);
                OutputStream os = client.getOutputStream();
                os.write("OPTIONS * RTSP/1.0\n".getBytes());
                os.write("CSeq: 1\n\n".getBytes());
                os.flush();

                //NOTE: it's very important to end any rtsp request with \n\n (two new lines). The server will acknowledge that the request ends there and it's time to send the response back.

                BufferedReader br =
                        new BufferedReader(
                                new InputStreamReader(
                                        new BufferedInputStream(client.getInputStream())));

                StringBuilder sb = new StringBuilder();
                String responseLine = null;

                while (null != (responseLine = br.readLine()))
                    sb.append(responseLine);
                String rtspResponse = sb.toString();
                if(rtspResponse.startsWith("RTSP/1.0 200 OK")){
                    // RTSP SERVER IS UP!!
                     handler.obtainMessage(MESSAGE_RTSP_OK).sendToTarget();
                } else {
                    // SOMETHING'S WRONG

                    handler.obtainMessage(MESSAGE_RTSP_ERROR).sendToTarget();
                }
                Log.d("RTSP reply" , rtspResponse);
                client.close();
            } catch (IOException e) {
                // NETWORK ERROR such as Timeout 
                e.printStackTrace();

                handler.obtainMessage(MESSAGE_RTSP_ERROR).sendToTarget();
            }

        }
    }.start();`
 
For this test I picked the public NASA TV rtsp server: rtsp://a1352.l1857053128.c18570.g.lq.akamaistream.net:554
 
The code sends the following rtsp request:
 
OPTIONS * RTSP/1.0 CSeq: 1
 
And receives the following response:
 
RTSP/1.0 200 OK Server: QTSS-Akamai/6.0.3 (Build/526.3; Platform/Linux; Release/Darwin; ) Cseq: 1 Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE, OPTIONS, ANNOUNCE, RECORD
 
If you are looking for more complex checks, feel free to dive into the rtsp protocol documentation and enhance the code per your own needs: https://www.ietf.org/rfc/rfc2326.txt
 
Please let me know if more information is needed.