谈Flash客户端与C++后台的几种通信方法

一，Flash 8以前时代：

??????? 使用AS2 API根据fscommand，以及SetVariable实现双工简单通信。当时这些小儿科的东西，我玩的不亦乐乎，还用在学校学生实验平台上。简单明了的SetVariable方法在AS3里面不能用了。特点：通信量小。

? ? Flash给C++传递参数：

fscommand("MsgBox","helloword");  

C++获取Flash传递的参数通过添加FSCommand消息函数来实现：

void CCppFlashDlg::FSCommandShockwaveflash1(LPCTSTR command,LPCTSTR args)
{
    if (0 == strcmp("MsgBox",command))
    {
        MessageBox(args);
    }
}

二，Flash 9以上AS3的ExternalInterface：

???????通过AS3的ExternalInterface调用C++中的函数，C++端通过Flash Player ActiveX控件中接口CallFunction调用AS3中的函数，值得注意的是，通信字符串格式都是XML格式，需要对XML文档进行解析。C++类的XML解析库有CMarkup和tinyXML。刚会了这些内容，我就用在了工业测控程序上，效果不错。特点：通信量小。

? ? C++调用Flash的函数必须先在Flash客户端里面注册，方法如下：

import mx.controls.Alert;
import flash.external.*;

ExternalInterface.addCallback("MsgBox2",this,MsgBox2);

function MsgBox2(msg:String)
{
    Alert.show(msg);
}

? ? ? 注册好以后VC即可调用Flash中的函数了，慢，不要着急，调用格式是XML的，所以需要多多学习XML文档的解析与生成：

void CCppFlashDlg::OnOK()
{
    swfUI.CallFunction("/
       <invoke name=/"MsgBox2/">/
           <arguments>/
               <string>Hi</string>/
           </arguments>/
       </invoke>");
}

三，通过Socket通信

?????? 建立Socket连接，需要特别处理Flash的安全策略文件。特点：通信量大，可以远程交互。

安全策略文件参考Flex Socket 与 C++ 通讯 --- 安全沙箱问题解决?

? ? ?其代码如下：

#include <winsock2.h>
#include <windows.h>
#include <iostream>
using namespace std;
#pragma comment(lib,"ws2_32.lib")

void main()
{ 
	WORD wVersionRequested;
	WSADATA wsaData;
	int err;
	short port=1800;//端口号
	
	wVersionRequested = MAKEWORD( 1,1 );
	err = WSAStartup( wVersionRequested,&wsaData );//初始化套接字
	if ( err != 0 )
	{
		return;
	}
	
	if ( LOBYTE( wsaData.wVersion ) != 1 || HIBYTE( wsaData.wVersion ) != 1 )
	{
		WSACleanup( );
		return;
	}
	
	SOCKET sockSrv=socket(AF_INET,SOCK_STREAM,0);//创建套接字
	SOCKET sockConn;//用来和客户端通信的套接字
	SOCKADDR_IN addrSrv;//用来和客户端通信的套接字地址
	addrSrv.sin_addr.S_un.S_addr=htonl(INADDR_ANY);
	addrSrv.sin_family=AF_INET;
	addrSrv.sin_port=htons(port);
	
	bind(sockSrv,(SOCKADDR*)&addrSrv,sizeof(SOCKADDR));//绑定端口
	listen(sockSrv,5);//侦听
	
	printf("Server %d is listening....../n",port);
	
	SOCKADDR_IN addrClient;
	
	int len=sizeof(SOCKADDR);
	char buf[4096];//接收的数据
	char rbuf[100]=
		"<cross-domain-policy> "  
		"<allow-access-from domain=/"*/" to-ports=/"*/"/>"  
		"</cross-domain-policy> ";//套接字策略文件
	
	while(1)
	{
        //接受连接
		sockConn=accept(sockSrv,(SOCKADDR*)&addrClient,&len);
		printf("Accept connection from %s/n",inet_ntoa(addrClient.sin_addr));
		
recv:
		//接收数据
		int bytes;
		if((bytes=recv(sockConn,buf,sizeof(buf),0))==SOCKET_ERROR)
		{
			printf("接收数据失败!/n");
			exit(-1);
		}

		buf[bytes]='/0';
		printf("Message from %s: %s/n",inet_ntoa(addrClient.sin_addr),buf);		

		if (0 == strcmp(buf,"<policy-file-request/>"))
		{
			//发送数据
			if(send(sockConn,rbuf,strlen(rbuf)+1,0)==SOCKET_ERROR)
			{
				printf("发送数据失败！");
				exit(-1);
			}
			printf("Message to %s: %s/n",rbuf);
		}
		else
		{
			//Echo
			if(send(sockConn,strlen(buf)+1,buf);
			goto recv;
		}
        //清理套接字占用的资源
        closesocket(sockConn);
	}
}

四，通过LocalConnection实现AS3与C++交互：

? ? Flash的LocalConnection是基于内存文件读写实现的。在C++客户端开启线程监视内存文件，获取Flash建立的LocalConnection，解析其发送的数据，需要了解Adobe的AMF格式。特点：限于一台电脑上通信。

? ? 假设仿真类已完成，并定义了消息：

#define WM_LOCAL_CONN_MESSAGE_IN			WM_USER+7	// A character was received and placed in the input buffer. 

? ? 当线程检测到Flash发送消息时 ，该仿真类派发该消息：

::SendMessage(pOwner->m_hWnd,WM_LOCAL_CONN_MESSAGE_IN,(WPARAM) msgRcv,(LPARAM) len);

? ? 在对话框类定义LocalConnectionEmulator实例，监测Flash的消息发送：

protected:
	LocalConnEmulator lcSim;

? ? 启动LocalConnection仿真程序：

lcSim.InitEmulator(this);
lcSim.StartEmulator();

? ? Flash客户端发送的信息的获取是通过仿真程序派发自定义事件捕获得到，定义自定义消息函数：

	// Generated message map functions
	virtual BOOL OnInitDialog();
	afx_msg LONG OnMessageIn(WPARAM arrayPtr,LPARAM len);
	afx_msg void OnSysCommand(UINT nID,LPARAM lParam);
	afx_msg void OnPaint();
	afx_msg HCURSOR OnQueryDragIcon();
	DECLARE_MESSAGE_MAP()

? ? 添加消息映射：

BEGIN_MESSAGE_MAP(CCppLocalConnDlg,CDialogEx)
	ON_MESSAGE(WM_LOCAL_CONN_MESSAGE_IN,OnMessageIn)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_BN_CLICKED(IDC_BUTTON1,&CCppLocalConnDlg::OnBnClickedButton1)
END_MESSAGE_MAP()

? ? 实现自定义消息函数：

LONG CCppLocalConnDlg::OnMessageIn(WPARAM arrayPtr,LPARAM len)
{
	char msgRcv[256];

	memcpy(msgRcv,(char*)arrayPtr,len);
	msgRcv[len]=0;

	this->SetWindowText(msgRcv);

	return true;
}

五，开源软件实现RTMP Server：

??????诸如CRTMP Server，openRTMFP。特点：很强大，易于实现音视频聊天类应用。总体而言CRTMP Server还支持远程共享对象的，功能更加强大，而且内存和CPU资源占用极小，一句话，好的没法说，但是openRTMFP可以通过lua脚本配置服务器，实现与Adobe Flash Media的类似脚本，也相当不错，这一点由于crtmpServer。

??? 如下为crtmpServer实现视频直播的demo，通过服务器直播摄像头内容（我使用虚拟摄像头，就是专门由来视频骗别人借钱汇款之类的软件），客户端为Adobe AS3API 文档中的例子：

package 
{
    import flash.display.Sprite;
    import flash.events.*;
    import flash.media.Video;
    import flash.media.Camera;
    import flash.net.NetConnection;
    import flash.net.NetStream;
    import fl.controls.Button;
    import fl.controls.Label;

    public class NetStream_publish extends Sprite 
    {
        private var connectionURL:String = "rtmp://127.0.0.1/live/";
        private var videoURL:String = "liveVideo";
        private var nc:NetConnection;
        private var ns_publish:NetStream;
        private var ns_playback:NetStream;
        private var video_publish:Video;
        private var video_playback:Video;
        private var cam:Camera;
        private var b:Button;
        private var l:Label;

        public function NetStream_publish() {
            setUpUI();
            
            nc = new NetConnection();
            nc.addEventListener(NetStatusEvent.NET_STATUS,netStatusHandler);
            
            // Add bandwidth detection handlers on the NetConnection Client to
            // prevent Reference Errors at runtime when using the "live" and "vod" applications.          
            var clientObj:Object = new Object();
            clientObj.onBWDone = onBWDone;
            clientObj.onBWCheck = onBWCheck;
            nc.client = clientObj;
            
            // Connect to the "live" application on Flash Media Server.
            nc.connect(connectionURL);
        }

        private function netStatusHandler(event:NetStatusEvent):void {
            trace(event.info.code + " | " + event.info.description);
            switch (event.info.code) {
                case "NetConnection.Connect.Success":
                    // Enable the "Publish" button after the client connects to the server.
                    b.enabled = true;
                    break;
                case "NetStream.Publish.Start":
                    playbackVideo();
                    break;
            }
        }
    
        private function publishVideo(event:MouseEvent):void{
            // Disable the button so that you can only publish once.
            b.enabled = false;
            // Create a NetStream to send video to FMS.
            ns_publish = new NetStream(nc);
            ns_publish.addEventListener(NetStatusEvent.NET_STATUS,netStatusHandler);
            // Publish (send) the video to FMS.
            cam = Camera.getCamera();
            ns_publish.attachCamera(cam);
               ns_publish.publish(videoURL);
        }

        private function playbackVideo():void {
            // Create the Video object to show the video on the stage
            video_playback = new Video(cam.width,cam.height);
            video_playback.x = cam.width + 20;
            video_playback.y = 10;
            addChild(video_playback);
            // Create a NetStream to receive the video from FMS.
            ns_playback = new NetStream(nc);
            ns_playback.addEventListener(NetStatusEvent.NET_STATUS,netStatusHandler);
            // Display the video that was published to FMS.
                  video_playback.attachNetStream(ns_playback);
            ns_playback.play(videoURL); 
        }
        
        
      private function setUpUI():void { 
      b = new Button(); 
      b.addEventListener(MouseEvent.CLICK,publishVideo);
      b.width = 150;
            b.label = "Publish video to server";
            b.move(10,150);
            b.enabled = false;
            
            l = new Label();
            l.width = 150;
            l.text = "Playing back from server"
            l.move(190,150);
            
            addChild(b);
            addChild(l);
        }
        
        // Handlers called by the Flash Media Server "live" and "vod" applications.
        public function onBWDone(... rest):Boolean {
            return true;
        }
        
        public function onBWCheck(... rest):Number {
            return 0;
        }
    }
}

??? 多个客户端连接，同时实现点播视频与在线视频流播放：

如下为openRTMFP(目前尚不支持远程共享对象)的使用实例，需要配置服务器（CumulusServer.ini）及基于lua脚本语言的服务器脚本（main.lua）：

;CumulusServer.ini
port = 1985 
udpBufferSize = 114688
keepAlivePeer = 10
keepAliveServer = 15
[logs]
name=log
directory=logs

? ? 服务器lua脚本如下：

function onStart(path)
	NOTE("Application '"..path.."' started")
end

function onStop(path)
	NOTE("Application '"..path.."' stopped")
end

function onConnection(client,userName,meeting)
	
	client.userName = userName;
	client.meeting = meeting;

	INFO("User connected: ",client.userName,"meeting: ",client.meeting);
	
	function client:getParticipants(meeting)
		result = {}
		i = 0;
		for key,cur_client in cumulus.clients:pairs() do
			if (cur_client.meeting == meeting) then
				i = i+1;
				participant = {};
				participant.userName = cur_client.userName;
				participant.meeting = cur_client.meeting;
				if cur_client.id then
					participant.protocol = 'rtmfp';
				end
				participant.farID = cur_client.id;			
				result[i] = participant;
			end
		end	
		return result;
	end
		
	function client:sendMessage(meeting,from,message)
		for key,cur_client in cumulus.clients:pairs() do
			if (cur_client.meeting == meeting) then		
				cur_client.writer:writeAMFMessage("onMessage",message);
			end
		end
	end

	sendParticipantUpdate(client.meeting);
end

function onDisconnection(client)
	INFO("User disconnecting: "..client.userName);
	sendParticipantUpdate(client.meeting);
end

function sendParticipantUpdate(meeting)
	for key,cur_client in cumulus.clients:pairs() do
		if (cur_client.meeting == meeting) then		
			cur_client.writer:writeAMFMessage("participantChanged");
		end
	end
end

? ? Flash聊天客户端软件下载：

基于openRTMFP的聊天应用?