mfc下tcp文件传输代码问题

guangmingdeshenju 2009-07-21 04:30:17

在网上下了个tcp文件传输源码，但发送端部分看不懂啊？？

DWORD CInstantmessageDlg:: SendFile(LPVOID lpParameter)

{

//PASS THE PARAMETER TO LOCAL VARIABLE

	HWND hwnd=((Parameter_socksend*)lpParameter)->hwnd;

    CString sendfname=((Parameter_socksend*)lpParameter)->sendfname;

	DWORD dwip=((Parameter_socksend*)lpParameter)->dwip;

	m_beginprgsend=TRUE;

	SOCKET socketsend=socket(AF_INET,SOCK_STREAM,0);

	

	SOCKADDR_IN addrSrv;

	addrSrv.sin_addr.S_un.S_addr=htonl(dwip);

	addrSrv.sin_family=AF_INET;

	addrSrv.sin_port=htons(4514);



	

    if(SOCKET_ERROR==connect(socketsend,(SOCKADDR*)&addrSrv,sizeof(SOCKADDR)))//CONNECT THE SPECIFIED DETINATION

	{

		closesocket(socketsend);

		::MessageBox(hwnd,"CONNECTION FAILED!","WARNING",MB_OK);

		return FALSE;

	}BOOL bRet = TRUE;

	

上满都是一些定义，没看头

下面才是最重要的啊	

    

   int fileLength, LeftToSend;

    int BytesSent;

    

    BYTE* sendData = NULL;CFile sourceFile;

    CFileException fe;

    BOOL FileIsOpen = FALSE;

    







    if( !( FileIsOpen = sourceFile.Open( sendfname, 

		CFile::modeRead | CFile::typeBinary, &fe ) ) )//问题一：这里面的条件具体指什么

    {

        TCHAR strCause[256];

        fe.GetErrorMessage( strCause, 255 );

        TRACE( "SendFileToRemoteRecipient encountered an error while opening the local file\n"

			"\tFile name = %s\n\tCause = %s\n\tm_cause = %d\n\tm_IOsError = %d\n",

			fe.m_strFileName, strCause, fe.m_cause, fe.m_lOsError );

//问题二：这个宏是干嘛的啊，还跟个数组



          bRet = FALSE;

        goto PreReturnCleanup;

    }

	

    

	fileLength = htonl( sourceFile.GetLength());

   

	 LeftToSend = sizeof( fileLength );

	

    do

    {

        

        BYTE* bp = (BYTE*)(&fileLength) + sizeof(fileLength) - LeftToSend;

        BytesSent = send(socketsend, (const char*)bp, LeftToSend,0 );

        

        

        if ( BytesSent == SOCKET_ERROR )

        {

            int iErr = ::GetLastError();

            TRACE( "SendFileToRemoteRecipient returned a socket error while sending file length\n"

                "\tNumber of Bytes sent = %d\n"

                "\tGetLastError = %d\n",BytesSent, iErr );

            

            

			

            bRet = FALSE;

            goto PreReturnCleanup;

        }

        

        

        LeftToSend -= BytesSent;

    }

    while ( LeftToSend>0 );

    

    

    sendData = new BYTE[SEND_BUFFER_SIZE]; 

    

   LeftToSend = sourceFile.GetLength();

    

    do

    {

       ::PostMessage(hwnd,UM_PRGSEND,0,(LPARAM)LeftToSend);

        

        int sendThisTime, doneSoFar, buffOffset;

        

        sendThisTime = sourceFile.Read( sendData, SEND_BUFFER_SIZE );

        buffOffset = 0;

        

        do

        {

            

			

			doneSoFar = send(socketsend,(const char*) (sendData + buffOffset), 

				sendThisTime,0 ); 

          

            

            if ( doneSoFar == SOCKET_ERROR )

            {

                int iErr = ::GetLastError();

                TRACE( "SendFileToRemoteRecipient returned a socket error while sending  file data\n"

					"\tNumber of Bytes sent = %d\n"

					"\tGetLastError = %d\n", doneSoFar, iErr );

				

				

				

				bRet = FALSE;

				goto PreReturnCleanup;

            }

            

            

            

            buffOffset += doneSoFar;

            sendThisTime -= doneSoFar;

           LeftToSend -= doneSoFar;

        }

        while ( sendThisTime > 0 );

        

    }

    while ( LeftToSend > 0 );

    

	

	

    

    PreReturnCleanup:				

    

    delete[] sendData;

    

    if ( FileIsOpen )

        sourceFile.Close();

	

	

	closesocket(socketsend);

    

    return bRet;

	

	}