一个基于JRTPLIB的轻量级RTSP客户端(myRTSPClient)——收流篇：（四）example代码解析

--------------------更新2018.08.20-------------------

添加http_tunnel_example.cpp作为RtspOverHttp示例程序。

--------------------更新2018.08.20结束-------------------

一、example逻辑伪码

myRTSPClient附带3个example程序：simple_example、complete_example、common_example。后两个example都是从simple_example中衍生出来的，以下将以simple_example为主进行解析，并且会在最后说明一下另两个example与simple_example的差别。

以下是simple_example简化后的伪代码，以便理解：

1. main():

2. 　　myRtspClient Client;

3. 　　Client.SetURI("rtsp://127.0.0.1/ansersion");

4. 　　Client.SendDESCRIBE();

5. 　　Client.SendSETUP();

6. 　　Client.SendPLAY();

7. 　　Write 1000 RTP Data to file "test_packet_recv.h264";

8. 　　Client.SendTEARDOWN();

9. 　　return;

二、simple_example.cpp代码注释

 #include <iostream>
 #include "rtspClient.h"
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>

 using std::cout;
 using std::endl;

 int main(int argc, char *argv[])
 {
         string RtspUri("rtsp://127.0.0.1/ansersion");
         // string RtspUri("rtsp://192.168.81.145/ansersion");
         RtspClient Client;

         /* Set up rtsp server resource URI */
         Client.SetURI(RtspUri);

         /* Send DESCRIBE command to server */
         Client.DoDESCRIBE();

         /* Parse SDP message after sending DESCRIBE command */
         Client.ParseSDP(); // 解析RTSP服务端受理DESCRIBE命令后返回的SDP信息

         /* Send SETUP command to set up all 'audio' and 'video'
          * sessions which SDP refers. */
         Client.DoSETUP();

         printf("start PLAY\n");
         printf("SDP: %s\n", Client.GetSDP().c_str());

         /* Send PLAY command to play only the
          * 'video' sessions.*/
         Client.DoPLAY("video");

         /* Receive 1000 RTP 'video' packets
          * note(FIXME):
          * if there are several 'video' session
          * refered in SDP, only receive packets of the first
          * 'video' session, the same as 'audio'.*/
         int packet_num = 0;
         uint8_t buf[65534];
         size_t size = 0;

         /* Write h264 video data to file "test_packet_recv.h264"
          * Then it could be played by ffplay */
         int fd = open("test_packet_recv.h264", O_CREAT | O_WRONLY | O_TRUNC, S_IRUSR | S_IWUSR | S_IXUSR);
         if(Client.GetSPSNalu(buf, &size)) { // 解码SDP中关于H264的SPS的数据
                 if(write(fd, buf, size) < 0) { // 将SPS写入文件
                         perror("write");
                 }
         } else {
                 printf("SPS error\n");
         }

         if(Client.GetPPSNalu(buf, &size)) { // 解码SDP中关于H264的PPS的数据
                 if(write(fd, buf, size) < 0) { // 将PPS写入文件
                         perror("write");
                 }
         } else {
                 printf("PPS error\n");
         }

         while(++packet_num < 1000) { // 接收1000个H264的数据包（确切的说是1000个NALU）
                 if(!Client.GetMediaData("video", buf, &size)) continue;
                 if(write(fd, buf, size) < 0) {
                         perror("write");
                 }
                 printf("recv %lu\n", size);
         }

         printf("start TEARDOWN\n");
         /* Send TEARDOWN command to teardown all of the sessions */
         Client.DoTEARDOWN();

         return 0;
 }
                               

三、common_example.cpp和complete_example.cpp

common_example.cpp不同于simple_example.cpp的地方只有开头几行，这些代码是为了可以用参数指定RTSP URI。

 int main(int argc, char *argv[])
 {
         if(argc != ) {
                 cout << "Usage: " << argv[] << " <URL>" << endl;
                 cout << "For example: " << endl;
                 cout << argv[] << " rtsp://127.0.0.1/ansersion" << endl;
                 return ;
         }
         cout << "Start play " << argv[] << endl;
         cout << "Then put video data into test_packet_recv.h264" << endl;
         string RtspUri(argv[]);
         // string RtspUri("rtsp://192.168.81.145/ansersion");
         RtspClient Client;

         /* Set up rtsp server resource URI */
         Client.SetURI(RtspUri);
         ......
         return ;
 }

complete_example.cpp不同于simple_example.cpp的地方，就在于每次发送RTSP命令时， 它都会检查命令发送是否成功，并且检验返回信息是否是“200 OK”。

 int main(int argc, char * argv[])
 {
         ......
          /* Send DESCRIBE command to server */
         if(Client.DoDESCRIBE() != RTSP_NO_ERROR) {
                 printf("DoDESCRIBE error\n");
                 return ;
         }
         printf("%s\n", Client.GetResponse().c_str());
         /* Check whether server return '200'(OK) */
         if(!Client.IsResponse_200_OK()) {
                 printf("DoDESCRIBE error\n");
                 return ;
         }
         ......
         return ;
 }

OK！以上便是myRTSP的基础内容。

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