Android WifiDisplay分析三：RTSP交互以及数据传输.docxVIP

前面我们分析到WifiDisplaySource会调用ANetworkSession的接口去创建一个socket，并在这个socket上监听是否有客户端的连接请求。先来看看Wifi Display规范的一些流程图：从之前的一篇文章中，当ANetworkSession创建好RTSP的listen socket后，就会把它加入到selelct中等待对方的连接，那我们首先来看ANetworkSession的threadLoop方法：javaview plaincopy1. voidANetworkSession:threadLoop()2. 3. intres=select(maxFd+1,&rs,&ws,NULL,NULL/*tv*/);4. 5. 6. Mutex:AutolockautoLock(mLock);7. 8. ListspsessionsToAdd;9. 10. for(size_ti=mSessions.size();res0&i-0;)11. constsp&session=mSessions.valueAt(i);12. 13. ints=session-socket();14. 15. if(sisRTSPServer()|session-isTCPDatagramServer()25. structsockaddr_inremoteAddr;26. socklen_tremoteAddrLen=sizeof(remoteAddr);27. 28. intclientSocket=accept(29. s,(structsockaddr*)&remoteAddr,&remoteAddrLen);30. 31. if(clientSocket=0)32. status_terr=MakeSocketNonBlocking(clientSocket);33. 34. if(err!=OK)35. 36. else37. in_addr_taddr=ntohl(remoteAddr.sin_addr.s_addr);38. 39. ALOGI(incomingconnectionfrom%d.%d.%d.%d:%d40. (socket%d),41. (addr24),42. (addr16)&0xff,43. (addr8)&0xff,44. addr&0xff,45. ntohs(remoteAddr.sin_port),46. clientSocket);47. 48. spclientSession=49. newSession(50. mNextSessionID+,51. Session:CONNECTED,52. clientSocket,53. session-getNotificationMessage();54. 55. clientSession-setMode(56. session-isRTSPServer()57. ?Session:MODE_RTSP58. :Session:MODE_DATAGRAM);59. 60. sessionsToAdd.push_back(clientSession);61. 62. else63. ALOGE(acceptreturnederror%d(%s),64. errno,strerror(errno);65. 66. 67. 68. 69. while(!sessionsToAdd.empty()70. spsession=*sessionsToAdd.begin();71. sessionsToAdd.erase(sessionsToAdd.begin();72. 73. mSessions.add(session-sessionID(),session);74. 75. ALOGI(addedclientSession%d,session-sessionID();76. 77. 上面在selelct循环中，首先只有刚创建的RTSP的listen socket，接着如果有客户端的连接请求，就会跳出select语句，然后调用accept去接收对方的连接。接着会去创建一个新的Session会话，我们去看它的构造函数：javaview plaincopy1. ANetworkSession:Session:Session(2. int32_tsessionID,3. Statestate,4. ints,5. constspify)6. :mSessionID(sessionID),7. mState(state),8. mMode(MODE_DATAGRAM),9. mSocket(s),10. mNotify(notify),11. mSawReceiveFailure(false),12. mSawSendFailure(false),13. mUDPRetries(kMaxUDPRetries),14. mLastStallReportUs(-1ll)15. if(mState=CONNECTED)16. structsockaddr_inlocalAddr;17. socklen_tlocalAddrLen=sizeof(localAddr);18. 19. intres=getsockname(20. mSocket,(structsockaddr*)&localAddr,&localAddrLen);21. CHECK_GE(res,0);22. 23. structsockaddr_inremoteAddr;24. socklen_tremoteAddrLen=sizeof(remoteAddr);25. 26. res=getpeername(27. mSocket,(structsockaddr*)&remoteAddr,&remoteAddrLen);28. CHECK_GE(res,0);29. 30. spmsg=mNotify-dup();31. msg-setInt32(sessionID,mSessionID);32. msg-setInt32(reason,kWhatClientConnected);33. msg-setString(server-ip,localAddrString.c_str();34. msg-setInt32(server-port,ntohs(localAddr.sin_port);35. msg-setString(client-ip,remoteAddrString.c_str();36. msg-setInt32(client-port,ntohs(remoteAddr.sin_port);37. msg-post();38. 39. 这里的状态mState为CONNECTED，所以会构建一个AMessage并post出去，由前一章的知识，我们知道这里的mNotify是一个kWhatRTSPNotify消息，会在WifiDisplaySource调用createRTSPServer时传进来的一个参数，所以这里创建的AMessage最终还是会被WifiDisplaySource去处理，跳过中间AMessage、ALooperRoster、ALooper的调用关系，我们直接到WifiDisplaySource的onMessageReceived去看如何处理：javaview plaincopy1. casekWhatRTSPNotify:2. 3. int32_treason;4. CHECK(msg-findInt32(reason,&reason);5. 6. switch(reason)7. caseANetworkSession:kWhatError:8. 9. 10. break;11. 12. 13. caseANetworkSession:kWhatClientConnected:14. 15. int32_tsessionID;16. CHECK(msg-findInt32(sessionID,&sessionID);17. 18. if(mClientSessionID0)19. ALOGW(Aclienttriedtoconnect,butwealready20. haveone.);21. 22. mNetSession-destroySession(sessionID);23. break;24. 25. 26. CHECK_EQ(mState,AWAITING_CLIENT_CONNECTION);27. 28. CHECK(msg-findString(client-ip,&mClientInfo.mRemoteIP);29. CHECK(msg-findString(server-ip,&mClientInfo.mLocalIP);30. 31. if(mClientInfo.mRemoteIP=mClientInfo.mLocalIP)32. /Disallowconnectionsfromthelocalinterface33. /forsecurityreasons.34. mNetSession-destroySession(sessionID);35. break;36. 37. 38. CHECK(msg-findInt32(39. server-port,&mClientInfo.mLocalPort);40. mClientInfo.mPlaybackSessionID=-1;41. 42. mClientSessionID=sessionID;43. 44. ALOGI(Wenowhaveaclient(%d)connected.,sessionID);45. 46. mState=AWAITING_CLIENT_SETUP;47. 48. status_terr=sendM1(sessionID);49. CHECK_EQ(err,(status_t)OK);50. break;51. 52. 53. caseANetworkSession:kWhatData:54. 55. 56. break;57. 58. 59. caseANetworkSession:kWhatNetworkStall:60. 61. break;62. 63. 64. default:65. TRESPASS();66. 67. break;68. 这里的reason是kWhatClientConnected，跳过前面不必要的case语句。如果先前已经连上其它的Sink device，这里就先断开之前的连接；如果没有，将新的SessionID赋予给mClientSessionID，并更改状态为AWAITING_CLIENT_SETUP，接着去看sendM1消息，这时候就要开始WifiDisplay M1M7消息的发送了。下面列举M1M7消息的格式，有兴趣的可以去对照代码分析，我们后面着重分析M6(SetUp)和M7(Play)两个消息。M1 reqeust:OPTIONS * RTSP/1.0Date: Tue, 29 Fri 2014 02:41:24 +0000Server: stagefright/1.2 (Linux;Android4.4)CSeq: 1Require: org.wfa.wfd1.0M1 respose:RTSP/1.0 200 OKCSeq: 1Date: Fri, Jan 01 2014 09:02:37 GMTPublic: org.wfa.wfd1.0, GET_PARAMETER, SET_PARAMETERM2 request:OPTIONS * RTSP/1.0CSeq: 2Require: org.wfa.wfd1.0M2 response:RTSP/1.0 200 OKDate: Tue, 29 Fri 2014 02:41:25 +0000Server: stagefright/1.2 (Linux;Android 4.3)CSeq: 2Public: org.wfa.wfd1.0, SETUP, TEARDOWN, PLAY, PAUSE, GET_PARAMETER, SET_PARAMETERM3 request:GET_PARAMETER rtsp:/localhost/wfd1.0 RTSP/1.0Date: Tue, 29 Fri 2014 02:41:25 +0000Server: stagefright/1.2 (Linux;Android 4.3)CSeq: 2Content-Type: text/parametersContent-Length: 83wfd_content_protectionwfd_video_formatswfd_audio_codecswfd_client_rtp_portsM3 response:RTSP/1.0 200 OKCSeq: 2Content-Length: 124Content-Type: text/parameterswfd_audio_codecs: LPCM 00000003 00, AAC 00000007 00wfd_video_formats: 00 00 02 02 0000FFFF 0FFFFFFF 00000FFF 00 0000 0000 01 none nonewfd_content_protection: nonewfd_client_rtp_ports: RTP/AVP/UDP;unicast 19990 0 mode=playM4 request:SET_PARAMETER rtsp:/localhost/wfd1.0 RTSP/1.0Date: Tue, 29 Fri 2014 02:41:25 +0000Server: stagefright/1.2 (Linux;Android 4.3)CSeq: 3Content-Type: text/parametersContent-Length: 247wfd_video_formats: 00 00 02 02 00000020 00000000 00000000 00 0000 0000 00 none nonewfd_audio_codecs: AAC 00000001 00wfd_presentation_URL: rtsp:/00/wfd1.0/streamid=0 nonewfd_client_rtp_ports: RTP/AVP/UDP;unicast 19990 0 mode=playM4 response:RTSP/1.0 200 OKCSeq: 3M5 request:SET_PARAMETER rtsp:/localhost/wfd1.0 RTSP/1.0Date: Tue, 29 Fri 2014 02:41:25 +0000Server: stagefright/1.2 (Linux;Android 4.3)CSeq: 4Content-Type: text/parametersContent-Length: 27wfd_trigger_method: SETUPM5 response:RTSP/1.0 200 OKCSeq: 4M6 request:SETUP rtsp:/00/wfd1.0/streamid=0 RTSP/1.0CSeq: 3Transport: RTP/AVP/UDP;unicast;client_port=19990M6 response:RTSP/1.0 200 OKDate: Tue, 29 Fri 2014 02:41:25 +0000Server: stagefright/1.2 (Linux;Android 4.3)CSeq: 3Session: 988982966;timeout=30Transport: RTP/AVP/UDP;unicast;client_port=19990;server_port=22220我们先来看处理M6 request的方法，代码在onSetupRequest中：javaview plaincopy1. status_tWifiDisplaySource:onSetupRequest(2. int32_tsessionID,3. int32_tcseq,4. constsp&data)5. CHECK_EQ(sessionID,mClientSessionID);6. if(mClientInfo.mPlaybackSessionID!=-1)7. sendErrorResponse(sessionID,400BadRequest,cseq);8. returnERROR_MALFORMED;9. 10. 11. int32_tplaybackSessionID=makeUniquePlaybackSessionID();12. 13. spnotify=newAMessage(kWhatPlaybackSessionNotify,id();14. notify-setInt32(playbackSessionID,playbackSessionID);15. notify-setInt32(sessionID,sessionID);16. 17. spplaybackSession=18. newPlaybackSession(19. mNetSession,notify,mInterfaceAddr,mHDCP,mMediaPath.c_str();20. 21. looper()-registerHandler(playbackSession);22. 23. AStringuri;24. data-getRequestField(1,&uri);25. 26. if(strncasecmp(rtsp:/,uri.c_str(),7)27. sendErrorResponse(sessionID,400BadRequest,cseq);28. returnERROR_MALFORMED;29. 30. 31. if(!(uri.startsWith(rtsp:/)&uri.endsWith(/wfd1.0/streamid=0)32. sendErrorResponse(sessionID,404Notfound,cseq);33. returnERROR_MALFORMED;34. 35. 36. RTPSender:TransportModertcpMode=RTPSender:TRANSPORT_UDP;37. if(clientRtcpinit(42. mClientInfo.mRemoteIP.c_str(),43. clientRtp,44. rtpMode,45. clientRtcp,46. rtcpMode,47. mSinkSupportsAudio,48. mUsingPCMAudio,49. mSinkSupportsVideo,50. mChosenVideoResolutionType,51. mChosenVideoResolutionIndex,52. mChosenVideoProfile,53. mChosenVideoLevel);54. 55. if(err!=OK)56. looper()-unregisterHandler(playbackSession-id();57. playbackSession.clear();58. 59. 60. mClientInfo.mPlaybackSessionID=playbackSessionID;61. mClientInfo.mPlaybackSession=playbackSession;62. 63. mState=AWAITING_CLI